Mercurial > cpython-lru_cache-weakref

annotate Lib/StringIO.py @ 14984:ece6c19edcc1 legacy-trunk

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Remove some debugging prints.
author Greg Ward <gward@python.net>
date Tue, 03 Oct 2000 03:32:37 +0000
parents b15fce868e50
children 3eb8687c98c6
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1 """File-like objects that read from or write to a string buffer.
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2
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3 This implements (nearly) all stdio methods.
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4
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5 f = StringIO() # ready for writing
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6 f = StringIO(buf) # ready for reading
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7 f.close() # explicitly release resources held
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8 flag = f.isatty() # always false
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9 pos = f.tell() # get current position
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10 f.seek(pos) # set current position
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11 f.seek(pos, mode) # mode 0: absolute; 1: relative; 2: relative to EOF
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12 buf = f.read() # read until EOF
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13 buf = f.read(n) # read up to n bytes
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14 buf = f.readline() # read until end of line ('\n') or EOF
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15 list = f.readlines()# list of f.readline() results until EOF
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16 f.truncate([size]) # truncate file at to at most size (default: current pos)
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17 f.write(buf) # write at current position
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18 f.writelines(list) # for line in list: f.write(line)
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19 f.getvalue() # return whole file's contents as a string
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20
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21 Notes:
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22 - Using a real file is often faster (but less convenient).
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23 - There's also a much faster implementation in C, called cStringIO, but
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24 it's not subclassable.
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25 - fileno() is left unimplemented so that code which uses it triggers
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26 an exception early.
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27 - Seeking far beyond EOF and then writing will insert real null
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28 bytes that occupy space in the buffer.
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29 - There's a simple test set (see end of this file).
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30 """
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31
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32 import errno
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33 import string
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34
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35 class StringIO:
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36 def __init__(self, buf = ''):
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37 self.buf = buf
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38 self.len = len(buf)
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39 self.buflist = []
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40 self.pos = 0
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41 self.closed = 0
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42 self.softspace = 0
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43 def close(self):
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44 if not self.closed:
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45 self.closed = 1
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46 del self.buf, self.pos
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47 def isatty(self):
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48 if self.closed:
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49 raise ValueError, "I/O operation on closed file"
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50 return 0
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51 def seek(self, pos, mode = 0):
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52 if self.closed:
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53 raise ValueError, "I/O operation on closed file"
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54 if self.buflist:
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55 self.buf = self.buf + string.joinfields(self.buflist, '')
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56 self.buflist = []
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57 if mode == 1:
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58 pos = pos + self.pos
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59 elif mode == 2:
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60 pos = pos + self.len
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61 self.pos = max(0, pos)
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62 def tell(self):
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63 if self.closed:
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64 raise ValueError, "I/O operation on closed file"
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65 return self.pos
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66 def read(self, n = -1):
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67 if self.closed:
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68 raise ValueError, "I/O operation on closed file"
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69 if self.buflist:
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70 self.buf = self.buf + string.joinfields(self.buflist, '')
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71 self.buflist = []
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72 if n < 0:
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73 newpos = self.len
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74 else:
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75 newpos = min(self.pos+n, self.len)
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76 r = self.buf[self.pos:newpos]
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77 self.pos = newpos
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78 return r
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79 def readline(self, length=None):
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80 if self.closed:
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81 raise ValueError, "I/O operation on closed file"
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82 if self.buflist:
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83 self.buf = self.buf + string.joinfields(self.buflist, '')
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84 self.buflist = []
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85 i = string.find(self.buf, '\n', self.pos)
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86 if i < 0:
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87 newpos = self.len
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88 else:
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89 newpos = i+1
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90 if length is not None:
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91 if self.pos + length < newpos:
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92 newpos = self.pos + length
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93 r = self.buf[self.pos:newpos]
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94 self.pos = newpos
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95 return r
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96 def readlines(self, sizehint = 0):
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97 total = 0
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98 lines = []
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99 line = self.readline()
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100 while line:
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101 lines.append(line)
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102 total += len(line)
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103 if 0 < sizehint <= total:
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104 break
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105 line = self.readline()
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106 return lines
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107 def truncate(self, size=None):
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108 if self.closed:
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109 raise ValueError, "I/O operation on closed file"
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110 if size is None:
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111 size = self.pos
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112 elif size < 0:
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113 raise IOError(errno.EINVAL,
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114 "Negative size not allowed")
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115 elif size < self.pos:
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116 self.pos = size
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117 self.buf = self.getvalue()[:size]
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118 def write(self, s):
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119 if self.closed:
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120 raise ValueError, "I/O operation on closed file"
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121 if not s: return
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122 if self.pos > self.len:
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123 self.buflist.append('\0'*(self.pos - self.len))
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124 self.len = self.pos
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125 newpos = self.pos + len(s)
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126 if self.pos < self.len:
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127 if self.buflist:
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128 self.buf = self.buf + string.joinfields(self.buflist, '')
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129 self.buflist = []
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130 self.buflist = [self.buf[:self.pos], s, self.buf[newpos:]]
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131 self.buf = ''
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132 else:
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133 self.buflist.append(s)
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134 self.len = newpos
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135 self.pos = newpos
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136 def writelines(self, list):
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137 self.write(string.joinfields(list, ''))
2852
1eeeba09a306 Added flush() method.
Sjoerd Mullender <sjoerd@acm.org>
parents: 2770
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138 def flush(self):
9016
b9a070736eac Raise the right exception (ValueError) for attempted I/O on closed StringIO
Fred Drake <fdrake@acm.org>
parents: 5898
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139 if self.closed:
b9a070736eac Raise the right exception (ValueError) for attempted I/O on closed StringIO
Fred Drake <fdrake@acm.org>
parents: 5898
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140 raise ValueError, "I/O operation on closed file"
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141 def getvalue(self):
3693
818ee115054a Sjoerd's StringIO speed-up
Guido van Rossum <guido@python.org>
parents: 3352
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142 if self.buflist:
818ee115054a Sjoerd's StringIO speed-up
Guido van Rossum <guido@python.org>
parents: 3352
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143 self.buf = self.buf + string.joinfields(self.buflist, '')
818ee115054a Sjoerd's StringIO speed-up
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parents: 3352
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144 self.buflist = []
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145 return self.buf
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146
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147
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148 # A little test suite
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149
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150 def test():
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151 import sys
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152 if sys.argv[1:]:
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153 file = sys.argv[1]
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
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154 else:
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
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155 file = '/etc/passwd'
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
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156 lines = open(file, 'r').readlines()
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157 text = open(file, 'r').read()
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158 f = StringIO()
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
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159 for line in lines[:-2]:
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160 f.write(line)
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161 f.writelines(lines[-2:])
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
parents:
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162 if f.getvalue() != text:
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
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163 raise RuntimeError, 'write failed'
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
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164 length = f.tell()
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165 print 'File length =', length
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
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166 f.seek(len(lines[0]))
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167 f.write(lines[1])
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
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168 f.seek(0)
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169 print 'First line =', `f.readline()`
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170 here = f.tell()
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171 line = f.readline()
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Guido van Rossum <guido@python.org>
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172 print 'Second line =', `line`
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
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173 f.seek(-len(line), 1)
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
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174 line2 = f.read(len(line))
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Guido van Rossum <guido@python.org>
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175 if line != line2:
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176 raise RuntimeError, 'bad result after seek back'
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
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177 f.seek(len(line2), 1)
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
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178 list = f.readlines()
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179 line = list[-1]
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180 f.seek(f.tell() - len(line))
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181 line2 = f.read()
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
parents:
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182 if line != line2:
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183 raise RuntimeError, 'bad result after seek back from EOF'
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
parents:
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184 print 'Read', len(list), 'more lines'
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
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185 print 'File length =', f.tell()
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
parents:
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186 if f.tell() != length:
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
parents:
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187 raise RuntimeError, 'bad length'
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
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188 f.close()
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
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189
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
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190 if __name__ == '__main__':
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
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191 test()