Mercurial > cpython-lru_cache-weakref

annotate Lib/StringIO.py @ 28646:193b8aec00ce legacy-trunk

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Changes from Jonathan Riehl to allow his pgen extension (PEP 269) to work. This includes some more code that used to be part of pgen in the main parser; I'm okay with that. I'll see if the Windows build needs work next.
author Guido van Rossum <guido@python.org>
date Thu, 17 Apr 2003 14:55:42 +0000
parents 31807880f599
children 3a99294c8e5b
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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 try:
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32 from errno import EINVAL
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33 except ImportError:
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34 EINVAL = 22
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35
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36 __all__ = ["StringIO"]
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37
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38 class StringIO:
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39 """class StringIO([buffer])
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40
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41 When a StringIO object is created, it can be initialized to an existing
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42 string by passing the string to the constructor. If no string is given,
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43 the StringIO will start empty.
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44
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45 The StringIO object can accept either Unicode or 8-bit strings, but
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46 mixing the two may take some care. If both are used, 8-bit strings that
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47 cannot be interpreted as 7-bit ASCII (that use the 8th bit) will cause
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48 a UnicodeError to be raised when getvalue() is called.
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49 """
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50 def __init__(self, buf = ''):
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51 # Force self.buf to be a string or unicode
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52 if not isinstance(buf, basestring):
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53 buf = str(buf)
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54 self.buf = buf
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55 self.len = len(buf)
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56 self.buflist = []
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57 self.pos = 0
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58 self.closed = 0
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59 self.softspace = 0
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60
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61 def __iter__(self):
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62 return self
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63
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64 def next(self):
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65 if self.closed:
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66 raise StopIteration
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67 r = self.readline()
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68 if not r:
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69 raise StopIteration
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70 return r
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71
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72 def close(self):
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73 """Free the memory buffer.
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74 """
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75 if not self.closed:
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76 self.closed = 1
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77 del self.buf, self.pos
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78
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79 def isatty(self):
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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 return False
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83
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84 def seek(self, pos, mode = 0):
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85 if self.closed:
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86 raise ValueError, "I/O operation on closed file"
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87 if self.buflist:
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88 self.buf += ''.join(self.buflist)
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89 self.buflist = []
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90 if mode == 1:
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91 pos += self.pos
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92 elif mode == 2:
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93 pos += self.len
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94 self.pos = max(0, pos)
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95
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96 def tell(self):
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97 if self.closed:
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98 raise ValueError, "I/O operation on closed file"
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99 return self.pos
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100
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101 def read(self, n = -1):
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102 if self.closed:
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103 raise ValueError, "I/O operation on closed file"
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104 if self.buflist:
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105 self.buf += ''.join(self.buflist)
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106 self.buflist = []
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107 if n < 0:
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108 newpos = self.len
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109 else:
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110 newpos = min(self.pos+n, self.len)
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111 r = self.buf[self.pos:newpos]
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112 self.pos = newpos
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113 return r
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114
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115 def readline(self, length=None):
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116 if self.closed:
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117 raise ValueError, "I/O operation on closed file"
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118 if self.buflist:
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119 self.buf += ''.join(self.buflist)
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120 self.buflist = []
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121 i = self.buf.find('\n', self.pos)
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122 if i < 0:
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123 newpos = self.len
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124 else:
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125 newpos = i+1
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126 if length is not None:
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127 if self.pos + length < newpos:
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128 newpos = self.pos + length
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129 r = self.buf[self.pos:newpos]
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130 self.pos = newpos
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131 return r
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132
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133 def readlines(self, sizehint = 0):
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134 total = 0
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parents: 15542
diff changeset
135 lines = []
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
136 line = self.readline()
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
137 while line:
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
138 lines.append(line)
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
139 total += len(line)
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
140 if 0 < sizehint <= total:
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Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
141 break
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diff changeset
142 line = self.readline()
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Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
143 return lines
15542
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parents: 15541
diff changeset
144
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parents: 15541
diff changeset
145 def truncate(self, size=None):
15555
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parents: 15542
diff changeset
146 if self.closed:
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Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
147 raise ValueError, "I/O operation on closed file"
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parents: 15542
diff changeset
148 if size is None:
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
149 size = self.pos
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diff changeset
150 elif size < 0:
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Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
151 raise IOError(EINVAL, "Negative size not allowed")
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Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
152 elif size < self.pos:
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Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
153 self.pos = size
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154 self.buf = self.getvalue()[:size]
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Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
155
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diff changeset
156 def write(self, s):
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Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
157 if self.closed:
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Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
158 raise ValueError, "I/O operation on closed file"
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Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
159 if not s: return
21656
6b0e16cb65d5 Restore Python 2.1 StringIO.py behaviour: support concatenating
Marc-André Lemburg <mal@egenix.com>
parents: 20060
diff changeset
160 # Force s to be a string or unicode
23645
e1e90b0f1f45 Remove uses of the string and types modules:
Walter Dörwald <walter@livinglogic.de>
parents: 23521
diff changeset
161 if not isinstance(s, basestring):
21656
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Marc-André Lemburg <mal@egenix.com>
parents: 20060
diff changeset
162 s = str(s)
25305
0399c8aea7b2 write(): Special case the common situation of a stream that's only
Fred Drake <fdrake@acm.org>
parents: 23645
diff changeset
163 if self.pos == self.len:
0399c8aea7b2 write(): Special case the common situation of a stream that's only
Fred Drake <fdrake@acm.org>
parents: 23645
diff changeset
164 self.buflist.append(s)
0399c8aea7b2 write(): Special case the common situation of a stream that's only
Fred Drake <fdrake@acm.org>
parents: 23645
diff changeset
165 self.len = self.pos = self.pos + len(s)
0399c8aea7b2 write(): Special case the common situation of a stream that's only
Fred Drake <fdrake@acm.org>
parents: 23645
diff changeset
166 return
15555
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diff changeset
167 if self.pos > self.len:
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parents: 15542
diff changeset
168 self.buflist.append('\0'*(self.pos - self.len))
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Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
169 self.len = self.pos
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Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
170 newpos = self.pos + len(s)
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Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
171 if self.pos < self.len:
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
172 if self.buflist:
16522
f42799c68929 Remove silly EMPTYSTRING global. Saves a global lookup.
Marc-André Lemburg <mal@egenix.com>
parents: 16070
diff changeset
173 self.buf += ''.join(self.buflist)
15555
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
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parents: 15542
diff changeset
174 self.buflist = []
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Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
175 self.buflist = [self.buf[:self.pos], s, self.buf[newpos:]]
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
176 self.buf = ''
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Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
177 if newpos > self.len:
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
178 self.len = newpos
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
179 else:
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
180 self.buflist.append(s)
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Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
181 self.len = newpos
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
182 self.pos = newpos
15542
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Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
183
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
184 def writelines(self, list):
16522
f42799c68929 Remove silly EMPTYSTRING global. Saves a global lookup.
Marc-André Lemburg <mal@egenix.com>
parents: 16070
diff changeset
185 self.write(''.join(list))
15542
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parents: 15541
diff changeset
186
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Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
187 def flush(self):
15555
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
188 if self.closed:
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
189 raise ValueError, "I/O operation on closed file"
15542
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Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
190
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
191 def getvalue(self):
23455
68c776ba5ea5 Added docstrings excerpted from Python Library Reference.
Raymond Hettinger <python@rcn.com>
parents: 23432
diff changeset
192 """
68c776ba5ea5 Added docstrings excerpted from Python Library Reference.
Raymond Hettinger <python@rcn.com>
parents: 23432
diff changeset
193 Retrieve the entire contents of the "file" at any time before
68c776ba5ea5 Added docstrings excerpted from Python Library Reference.
Raymond Hettinger <python@rcn.com>
parents: 23432
diff changeset
194 the StringIO object's close() method is called.
68c776ba5ea5 Added docstrings excerpted from Python Library Reference.
Raymond Hettinger <python@rcn.com>
parents: 23432
diff changeset
195
68c776ba5ea5 Added docstrings excerpted from Python Library Reference.
Raymond Hettinger <python@rcn.com>
parents: 23432
diff changeset
196 The StringIO object can accept either Unicode or 8-bit strings,
68c776ba5ea5 Added docstrings excerpted from Python Library Reference.
Raymond Hettinger <python@rcn.com>
parents: 23432
diff changeset
197 but mixing the two may take some care. If both are used, 8-bit
68c776ba5ea5 Added docstrings excerpted from Python Library Reference.
Raymond Hettinger <python@rcn.com>
parents: 23432
diff changeset
198 strings that cannot be interpreted as 7-bit ASCII (that use the
68c776ba5ea5 Added docstrings excerpted from Python Library Reference.
Raymond Hettinger <python@rcn.com>
parents: 23432
diff changeset
199 8th bit) will cause a UnicodeError to be raised when getvalue()
23521
a90faa5f9417 Whitespace normalization.
Tim Peters <tim.peters@gmail.com>
parents: 23455
diff changeset
200 is called.
23455
68c776ba5ea5 Added docstrings excerpted from Python Library Reference.
Raymond Hettinger <python@rcn.com>
parents: 23432
diff changeset
201 """
15555
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
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diff changeset
202 if self.buflist:
16522
f42799c68929 Remove silly EMPTYSTRING global. Saves a global lookup.
Marc-André Lemburg <mal@egenix.com>
parents: 16070
diff changeset
203 self.buf += ''.join(self.buflist)
15555
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
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parents: 15542
diff changeset
204 self.buflist = []
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
205 return self.buf
1680
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
parents:
diff changeset
206
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
parents:
diff changeset
207
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
parents:
diff changeset
208 # A little test suite
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
parents:
diff changeset
209
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
parents:
diff changeset
210 def test():
15542
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parents: 15541
diff changeset
211 import sys
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
212 if sys.argv[1:]:
15555
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
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parents: 15542
diff changeset
213 file = sys.argv[1]
15542
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
214 else:
15555
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
215 file = '/etc/passwd'
15542
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Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
216 lines = open(file, 'r').readlines()
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
217 text = open(file, 'r').read()
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
218 f = StringIO()
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
219 for line in lines[:-2]:
15555
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
220 f.write(line)
15542
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
221 f.writelines(lines[-2:])
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
222 if f.getvalue() != text:
15555
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
223 raise RuntimeError, 'write failed'
15542
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
224 length = f.tell()
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
225 print 'File length =', length
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
226 f.seek(len(lines[0]))
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
227 f.write(lines[1])
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
228 f.seek(0)
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
229 print 'First line =', `f.readline()`
21915
e163713b47cf SF #515000, print result of f.tell() in test() instead of ignoring
Neal Norwitz <nnorwitz@gmail.com>
parents: 21656
diff changeset
230 print 'Position =', f.tell()
15542
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
231 line = f.readline()
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
232 print 'Second line =', `line`
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
233 f.seek(-len(line), 1)
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
234 line2 = f.read(len(line))
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
235 if line != line2:
15555
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
236 raise RuntimeError, 'bad result after seek back'
15542
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
237 f.seek(len(line2), 1)
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
238 list = f.readlines()
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
239 line = list[-1]
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
240 f.seek(f.tell() - len(line))
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
241 line2 = f.read()
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
242 if line != line2:
15555
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
243 raise RuntimeError, 'bad result after seek back from EOF'
15542
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
244 print 'Read', len(list), 'more lines'
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
245 print 'File length =', f.tell()
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
246 if f.tell() != length:
15555
f72345b43662 Untabify! (Barry, this is gonna cost you a bottle of wine! ;)
Fred Drake <fdrake@acm.org>
parents: 15542
diff changeset
247 raise RuntimeError, 'bad length'
15542
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
248 f.close()
1680
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
parents:
diff changeset
249
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
parents:
diff changeset
250 if __name__ == '__main__':
15542
6359480106ec Change the file's indentation from tabs to 4 spaces per level.
Barry Warsaw <barry@python.org>
parents: 15541
diff changeset
251 test()