Mercurial > cpython-lru_cache-weakref

annotate Lib/csv.py @ 51749:1408feec0084 3.0

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Merged revisions 69798 via svnmerge from svn+ssh://pythondev@svn.python.org/python/branches/py3k ................ r69798 | benjamin.peterson | 2009-02-19 22:02:38 -0600 (Thu, 19 Feb 2009) | 13 lines Merged revisions 69769,69776 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r69769 | georg.brandl | 2009-02-19 02:30:06 -0600 (Thu, 19 Feb 2009) | 1 line #5310, #3558: fix operator precedence table. ........ r69776 | georg.brandl | 2009-02-19 10:34:51 -0600 (Thu, 19 Feb 2009) | 2 lines #5317: update IronPython URL. ........ ................
author Benjamin Peterson <benjamin@python.org>
date Fri, 20 Feb 2009 04:05:32 +0000
parents edb5a8593749
children c9bd62efe6ce
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1
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2 """
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3 csv.py - read/write/investigate CSV files
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4 """
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5
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6 import re
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7 from _csv import Error, __version__, writer, reader, register_dialect, \
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8 unregister_dialect, get_dialect, list_dialects, \
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9 field_size_limit, \
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10 QUOTE_MINIMAL, QUOTE_ALL, QUOTE_NONNUMERIC, QUOTE_NONE, \
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11 __doc__
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12 from _csv import Dialect as _Dialect
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13
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14 from io import StringIO
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15
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16 __all__ = [ "QUOTE_MINIMAL", "QUOTE_ALL", "QUOTE_NONNUMERIC", "QUOTE_NONE",
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17 "Error", "Dialect", "__doc__", "excel", "excel_tab",
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18 "field_size_limit", "reader", "writer",
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19 "register_dialect", "get_dialect", "list_dialects", "Sniffer",
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20 "unregister_dialect", "__version__", "DictReader", "DictWriter" ]
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21
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22 class Dialect:
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23 """Describe an Excel dialect.
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24
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25 This must be subclassed (see csv.excel). Valid attributes are:
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26 delimiter, quotechar, escapechar, doublequote, skipinitialspace,
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27 lineterminator, quoting.
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28
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29 """
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30 _name = ""
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31 _valid = False
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32 # placeholders
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33 delimiter = None
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34 quotechar = None
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35 escapechar = None
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36 doublequote = None
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37 skipinitialspace = None
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38 lineterminator = None
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39 quoting = None
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40
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41 def __init__(self):
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42 if self.__class__ != Dialect:
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43 self._valid = True
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44 self._validate()
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45
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46 def _validate(self):
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47 try:
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48 _Dialect(self)
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49 except TypeError as e:
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50 # We do this for compatibility with py2.3
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51 raise Error(str(e))
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52
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53 class excel(Dialect):
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54 """Describe the usual properties of Excel-generated CSV files."""
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55 delimiter = ','
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56 quotechar = '"'
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57 doublequote = True
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58 skipinitialspace = False
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59 lineterminator = '\r\n'
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60 quoting = QUOTE_MINIMAL
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61 register_dialect("excel", excel)
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62
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63 class excel_tab(excel):
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64 """Describe the usual properties of Excel-generated TAB-delimited files."""
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65 delimiter = '\t'
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66 register_dialect("excel-tab", excel_tab)
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67
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68
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69 class DictReader:
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70 def __init__(self, f, fieldnames=None, restkey=None, restval=None,
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71 dialect="excel", *args, **kwds):
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72 self._fieldnames = fieldnames # list of keys for the dict
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73 self.restkey = restkey # key to catch long rows
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74 self.restval = restval # default value for short rows
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75 self.reader = reader(f, dialect, *args, **kwds)
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76 self.dialect = dialect
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77 self.line_num = 0
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78
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79 def __iter__(self):
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80 return self
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81
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82 @property
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83 def fieldnames(self):
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84 if self._fieldnames is None:
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85 try:
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86 self._fieldnames = next(self.reader)
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87 except StopIteration:
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88 pass
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89 self.line_num = self.reader.line_num
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90 return self._fieldnames
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91
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92 @fieldnames.setter
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93 def fieldnames(self, value):
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94 self._fieldnames = value
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95
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96 def __next__(self):
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97 if self.line_num == 0:
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98 # Used only for its side effect.
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99 self.fieldnames
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100 row = next(self.reader)
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101 self.line_num = self.reader.line_num
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102
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103 # unlike the basic reader, we prefer not to return blanks,
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104 # because we will typically wind up with a dict full of None
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105 # values
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106 while row == []:
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107 row = next(self.reader)
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108 d = dict(zip(self.fieldnames, row))
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109 lf = len(self.fieldnames)
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110 lr = len(row)
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111 if lf < lr:
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112 d[self.restkey] = row[lf:]
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113 elif lf > lr:
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114 for key in self.fieldnames[lr:]:
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115 d[key] = self.restval
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116 return d
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117
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118
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119 class DictWriter:
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120 def __init__(self, f, fieldnames, restval="", extrasaction="raise",
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121 dialect="excel", *args, **kwds):
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122 self.fieldnames = fieldnames # list of keys for the dict
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123 self.restval = restval # for writing short dicts
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124 if extrasaction.lower() not in ("raise", "ignore"):
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125 raise ValueError("extrasaction (%s) must be 'raise' or 'ignore'"
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126 % extrasaction)
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127 self.extrasaction = extrasaction
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128 self.writer = writer(f, dialect, *args, **kwds)
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129
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130 def _dict_to_list(self, rowdict):
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131 if self.extrasaction == "raise":
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132 wrong_fields = [k for k in rowdict if k not in self.fieldnames]
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133 if wrong_fields:
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134 raise ValueError("dict contains fields not in fieldnames: "
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135 + ", ".join(wrong_fields))
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136 return [rowdict.get(key, self.restval) for key in self.fieldnames]
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137
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138 def writerow(self, rowdict):
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139 return self.writer.writerow(self._dict_to_list(rowdict))
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140
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141 def writerows(self, rowdicts):
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142 rows = []
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143 for rowdict in rowdicts:
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144 rows.append(self._dict_to_list(rowdict))
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145 return self.writer.writerows(rows)
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146
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147 # Guard Sniffer's type checking against builds that exclude complex()
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148 try:
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149 complex
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150 except NameError:
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151 complex = float
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152
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153 class Sniffer:
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154 '''
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155 "Sniffs" the format of a CSV file (i.e. delimiter, quotechar)
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156 Returns a Dialect object.
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157 '''
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158 def __init__(self):
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159 # in case there is more than one possible delimiter
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160 self.preferred = [',', '\t', ';', ' ', ':']
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161
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162
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163 def sniff(self, sample, delimiters=None):
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164 """
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165 Returns a dialect (or None) corresponding to the sample
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166 """
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167
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168 quotechar, delimiter, skipinitialspace = \
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169 self._guess_quote_and_delimiter(sample, delimiters)
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96eb2a5cfbef Fix a delimiter detection problem in sniffer. Sniffing "a|b|c\r\n" was
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170 if not delimiter:
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171 delimiter, skipinitialspace = self._guess_delimiter(sample,
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172 delimiters)
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173
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174 if not delimiter:
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907a45df1295 Raise statement normalization in Lib/.
Collin Winter <collinw@gmail.com>
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175 raise Error("Could not determine delimiter")
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176
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177 class dialect(Dialect):
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178 _name = "sniffed"
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179 lineterminator = '\r\n'
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2fad548391de Attempt to deal with some obvious errors in the code. These were all
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180 quoting = QUOTE_MINIMAL
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181 # escapechar = ''
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182 doublequote = False
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183
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184 dialect.delimiter = delimiter
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185 # _csv.reader won't accept a quotechar of ''
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186 dialect.quotechar = quotechar or '"'
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187 dialect.skipinitialspace = skipinitialspace
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188
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189 return dialect
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190
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191
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192 def _guess_quote_and_delimiter(self, data, delimiters):
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193 """
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194 Looks for text enclosed between two identical quotes
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195 (the probable quotechar) which are preceded and followed
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196 by the same character (the probable delimiter).
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197 For example:
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198 ,'some text',
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199 The quote with the most wins, same with the delimiter.
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200 If there is no quotechar the delimiter can't be determined
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201 this way.
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202 """
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203
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204 matches = []
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205 for restr in ('(?P<delim>[^\w\n"\'])(?P<space> ?)(?P<quote>["\']).*?(?P=quote)(?P=delim)', # ,".*?",
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206 '(?:^|\n)(?P<quote>["\']).*?(?P=quote)(?P<delim>[^\w\n"\'])(?P<space> ?)', # ".*?",
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207 '(?P<delim>>[^\w\n"\'])(?P<space> ?)(?P<quote>["\']).*?(?P=quote)(?:$|\n)', # ,".*?"
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208 '(?:^|\n)(?P<quote>["\']).*?(?P=quote)(?:$|\n)'): # ".*?" (no delim, no space)
30292
79b1a9ec5223 use the long names for re compilation options; this makes it easier to
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209 regexp = re.compile(restr, re.DOTALL | re.MULTILINE)
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210 matches = regexp.findall(data)
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211 if matches:
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212 break
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213
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214 if not matches:
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215 return ('', None, 0) # (quotechar, delimiter, skipinitialspace)
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216
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217 quotes = {}
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218 delims = {}
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219 spaces = 0
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220 for m in matches:
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221 n = regexp.groupindex['quote'] - 1
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222 key = m[n]
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223 if key:
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224 quotes[key] = quotes.get(key, 0) + 1
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225 try:
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226 n = regexp.groupindex['delim'] - 1
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227 key = m[n]
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228 except KeyError:
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229 continue
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434ef174f478 * Correct Sniffer doc to correspond to the implementation.
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230 if key and (delimiters is None or key in delimiters):
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231 delims[key] = delims.get(key, 0) + 1
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232 try:
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233 n = regexp.groupindex['space'] - 1
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234 except KeyError:
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235 continue
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236 if m[n]:
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237 spaces += 1
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238
39627
e86c0b29b4a2 Kill reduce(). A coproduction of John Reese, Jacques Frechet, and Alex M.
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239 quotechar = max(quotes, key=quotes.get)
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240
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241 if delims:
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e86c0b29b4a2 Kill reduce(). A coproduction of John Reese, Jacques Frechet, and Alex M.
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parents: 36157
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242 delim = max(delims, key=delims.get)
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243 skipinitialspace = delims[delim] == spaces
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244 if delim == '\n': # most likely a file with a single column
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245 delim = ''
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246 else:
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247 # there is *no* delimiter, it's a single column of quoted data
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248 delim = ''
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249 skipinitialspace = 0
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250
0c950e3323ee cvs is going to be a module again
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251 return (quotechar, delim, skipinitialspace)
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252
0c950e3323ee cvs is going to be a module again
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253
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254 def _guess_delimiter(self, data, delimiters):
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255 """
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256 The delimiter /should/ occur the same number of times on
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257 each row. However, due to malformed data, it may not. We don't want
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258 an all or nothing approach, so we allow for small variations in this
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259 number.
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260 1) build a table of the frequency of each character on every line.
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261 2) build a table of freqencies of this frequency (meta-frequency?),
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262 e.g. 'x occurred 5 times in 10 rows, 6 times in 1000 rows,
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263 7 times in 2 rows'
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264 3) use the mode of the meta-frequency to determine the /expected/
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265 frequency for that character
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266 4) find out how often the character actually meets that goal
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267 5) the character that best meets its goal is the delimiter
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268 For performance reasons, the data is evaluated in chunks, so it can
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269 try and evaluate the smallest portion of the data possible, evaluating
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270 additional chunks as necessary.
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271 """
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272
42142
a53e48be6df9 Merged revisions 56125-56153 via svnmerge from
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273 data = list(filter(None, data.split('\n')))
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274
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275 ascii = [chr(c) for c in range(127)] # 7-bit ASCII
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276
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277 # build frequency tables
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278 chunkLength = min(10, len(data))
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279 iteration = 0
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280 charFrequency = {}
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281 modes = {}
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282 delims = {}
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283 start, end = 0, min(chunkLength, len(data))
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284 while start < len(data):
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285 iteration += 1
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286 for line in data[start:end]:
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287 for char in ascii:
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288 metaFrequency = charFrequency.get(char, {})
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289 # must count even if frequency is 0
36146
22dbf5818b0b Fix for problem with Sniffer class. If your delimiter is whitespace and the
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290 freq = line.count(char)
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291 # value is the mode
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292 metaFrequency[freq] = metaFrequency.get(freq, 0) + 1
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293 charFrequency[char] = metaFrequency
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294
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295 for char in charFrequency.keys():
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296 items = list(charFrequency[char].items())
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297 if len(items) == 1 and items[0][0] == 0:
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298 continue
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299 # get the mode of the frequencies
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300 if len(items) > 1:
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301 modes[char] = max(items, key=lambda x: x[1])
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302 # adjust the mode - subtract the sum of all
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303 # other frequencies
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304 items.remove(modes[char])
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305 modes[char] = (modes[char][0], modes[char][1]
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306 - sum(item[1] for item in items))
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307 else:
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308 modes[char] = items[0]
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309
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310 # build a list of possible delimiters
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311 modeList = modes.items()
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312 total = float(chunkLength * iteration)
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313 # (rows of consistent data) / (number of rows) = 100%
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314 consistency = 1.0
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315 # minimum consistency threshold
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316 threshold = 0.9
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317 while len(delims) == 0 and consistency >= threshold:
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318 for k, v in modeList:
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319 if v[0] > 0 and v[1] > 0:
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434ef174f478 * Correct Sniffer doc to correspond to the implementation.
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320 if ((v[1]/total) >= consistency and
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321 (delimiters is None or k in delimiters)):
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322 delims[k] = v
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323 consistency -= 0.01
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324
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325 if len(delims) == 1:
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326 delim = list(delims.keys())[0]
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327 skipinitialspace = (data[0].count(delim) ==
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328 data[0].count("%c " % delim))
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329 return (delim, skipinitialspace)
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330
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331 # analyze another chunkLength lines
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332 start = end
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333 end += chunkLength
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334
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335 if not delims:
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336 return ('', 0)
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337
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338 # if there's more than one, fall back to a 'preferred' list
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339 if len(delims) > 1:
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340 for d in self.preferred:
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341 if d in delims.keys():
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342 skipinitialspace = (data[0].count(d) ==
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343 data[0].count("%c " % d))
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344 return (d, skipinitialspace)
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345
36157
96eb2a5cfbef Fix a delimiter detection problem in sniffer. Sniffing "a|b|c\r\n" was
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346 # nothing else indicates a preference, pick the character that
96eb2a5cfbef Fix a delimiter detection problem in sniffer. Sniffing "a|b|c\r\n" was
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347 # dominates(?)
96eb2a5cfbef Fix a delimiter detection problem in sniffer. Sniffing "a|b|c\r\n" was
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348 items = [(v,k) for (k,v) in delims.items()]
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349 items.sort()
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350 delim = items[-1][1]
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351
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352 skipinitialspace = (data[0].count(delim) ==
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353 data[0].count("%c " % delim))
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354 return (delim, skipinitialspace)
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355
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356
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357 def has_header(self, sample):
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358 # Creates a dictionary of types of data in each column. If any
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359 # column is of a single type (say, integers), *except* for the first
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360 # row, then the first row is presumed to be labels. If the type
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361 # can't be determined, it is assumed to be a string in which case
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362 # the length of the string is the determining factor: if all of the
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363 # rows except for the first are the same length, it's a header.
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364 # Finally, a 'vote' is taken at the end for each column, adding or
0c950e3323ee cvs is going to be a module again
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365 # subtracting from the likelihood of the first row being a header.
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366
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367 rdr = reader(StringIO(sample), self.sniff(sample))
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368
41501
0c5019afc55b PEP 3114: rename .next() to .__next__() and add next() builtin.
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369 header = next(rdr) # assume first row is header
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370
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371 columns = len(header)
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372 columnTypes = {}
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373 for i in range(columns): columnTypes[i] = None
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374
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375 checked = 0
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376 for row in rdr:
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377 # arbitrary number of rows to check, to keep it sane
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378 if checked > 20:
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379 break
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380 checked += 1
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381
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382 if len(row) != columns:
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383 continue # skip rows that have irregular number of columns
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384
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385 for col in list(columnTypes.keys()):
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bac2c0e7c20a SF Patch #744104: Remove eval() from csv
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diff changeset
386
46548
85d4671565c8 Obvious simplification, now that "long" has disappeared.
Amaury Forgeot d'Arc <amauryfa@gmail.com>
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387 for thisType in [int, float, complex]:
28804
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388 try:
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bac2c0e7c20a SF Patch #744104: Remove eval() from csv
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diff changeset
389 thisType(row[col])
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diff changeset
390 break
29420
f87fcd0870bf The multiple exception catch should be in a tuple.
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diff changeset
391 except (ValueError, OverflowError):
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bac2c0e7c20a SF Patch #744104: Remove eval() from csv
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diff changeset
392 pass
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diff changeset
393 else:
28804
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394 # fallback to length of string
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395 thisType = len(row[col])
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396
0c950e3323ee cvs is going to be a module again
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397 if thisType != columnTypes[col]:
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398 if columnTypes[col] is None: # add new column type
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399 columnTypes[col] = thisType
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400 else:
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401 # type is inconsistent, remove column from
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402 # consideration
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403 del columnTypes[col]
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parents:
diff changeset
404
0c950e3323ee cvs is going to be a module again
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parents:
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405 # finally, compare results against first row and "vote"
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406 # on whether it's a header
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407 hasHeader = 0
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408 for col, colType in columnTypes.items():
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409 if type(colType) == type(0): # it's a length
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parents:
diff changeset
410 if len(header[col]) != colType:
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411 hasHeader += 1
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412 else:
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413 hasHeader -= 1
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414 else: # attempt typecast
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parents:
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415 try:
29411
bac2c0e7c20a SF Patch #744104: Remove eval() from csv
Raymond Hettinger <python@rcn.com>
parents: 29169
diff changeset
416 colType(header[col])
29422
cf8ae3b0dcdc One more multiple exception catch should be in a tuple.
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parents: 29420
diff changeset
417 except (ValueError, TypeError):
28804
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418 hasHeader += 1
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419 else:
0c950e3323ee cvs is going to be a module again
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420 hasHeader -= 1
0c950e3323ee cvs is going to be a module again
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421
0c950e3323ee cvs is going to be a module again
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422 return hasHeader > 0