Mercurial > cpython-lru_cache-weakref

annotate Lib/StringIO.py @ 3044:7e7bb00a0a2e legacy-trunk

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Added functionality: locate CW projects, copy them, empty them and binhex them.
author Jack Jansen <jack.jansen@cwi.nl>
date Thu, 31 Aug 1995 13:47:14 +0000
parents 1eeeba09a306
children 81f45f69388e
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
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1 # class StringIO implements file-like objects that read/write a
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2 # string buffer (a.k.a. "memory files").
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3 #
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4 # This implements (nearly) all stdio methods.
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5 #
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6 # f = StringIO() # ready for writing
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7 # f = StringIO(buf) # ready for reading
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8 # f.close() # explicitly release resources held
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9 # flag = f.isatty() # always false
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10 # pos = f.tell() # get current position
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11 # f.seek(pos) # set current position
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12 # f.seek(pos, mode) # mode 0: absolute; 1: relative; 2: relative to EOF
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13 # buf = f.read() # read until EOF
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14 # buf = f.read(n) # read up to n bytes
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15 # buf = f.readline() # read until end of line ('\n') or EOF
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16 # list = f.readlines()# list of f.readline() results until EOF
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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 # - fileno() is left unimplemented so that code which uses it triggers
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24 # an exception early.
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25 # - Seeking far beyond EOF and then writing will insert real null
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26 # bytes that occupy space in the buffer.
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27 # - There's a simple test set (see end of this file).
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28
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29 import string
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30
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31 class StringIO:
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32 def __init__(self, buf = ''):
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33 self.buf = buf
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34 self.pos = 0
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35 self.closed = 0
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36 self.softspace = 0
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37 def close(self):
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38 if not self.closed:
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39 self.closed = 1
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40 del self.buf, self.pos
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41 def isatty(self):
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42 return 0
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43 def seek(self, pos, mode = 0):
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44 if mode == 1:
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45 pos = pos + self.pos
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46 elif mode == 2:
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47 pos = pos + len(self.buf)
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48 self.pos = max(0, pos)
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49 def tell(self):
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50 return self.pos
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51 def read(self, n = 0):
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52 if n <= 0:
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53 newpos = len(self.buf)
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54 else:
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55 newpos = min(self.pos+n, len(self.buf))
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56 r = self.buf[self.pos:newpos]
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57 self.pos = newpos
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58 return r
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59 def readline(self):
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60 i = string.find(self.buf, '\n', self.pos)
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61 if i < 0:
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62 newpos = len(self.buf)
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63 else:
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64 newpos = i+1
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65 r = self.buf[self.pos:newpos]
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66 self.pos = newpos
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67 return r
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68 def readlines(self):
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69 lines = []
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70 line = self.readline()
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71 while line:
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72 lines.append(line)
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73 line = self.readline()
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74 return lines
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75 def write(self, s):
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76 if not s: return
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77 if self.pos > len(self.buf):
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78 self.buf = self.buf + '\0'*(self.pos - len(self.buf))
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79 newpos = self.pos + len(s)
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80 self.buf = self.buf[:self.pos] + s + self.buf[newpos:]
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81 self.pos = newpos
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82 def writelines(self, list):
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83 self.write(string.joinfields(list, ''))
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84 def flush(self):
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85 pass
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86 def getvalue(self):
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87 return self.buf
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88
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89
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90 # A little test suite
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91
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92 def test():
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93 import sys
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94 if sys.argv[1:]:
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95 file = sys.argv[1]
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96 else:
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97 file = '/etc/passwd'
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98 lines = open(file, 'r').readlines()
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99 text = open(file, 'r').read()
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100 f = StringIO()
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101 for line in lines[:-2]:
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102 f.write(line)
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103 f.writelines(lines[-2:])
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104 if f.getvalue() != text:
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105 raise RuntimeError, 'write failed'
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106 length = f.tell()
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107 print 'File length =', length
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108 f.seek(len(lines[0]))
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109 f.write(lines[1])
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110 f.seek(0)
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111 print 'First line =', `f.readline()`
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112 here = f.tell()
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113 line = f.readline()
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114 print 'Second line =', `line`
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115 f.seek(-len(line), 1)
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116 line2 = f.read(len(line))
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117 if line != line2:
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118 raise RuntimeError, 'bad result after seek back'
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119 f.seek(len(line2), 1)
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120 list = f.readlines()
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121 line = list[-1]
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122 f.seek(f.tell() - len(line))
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123 line2 = f.read()
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124 if line != line2:
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125 raise RuntimeError, 'bad result after seek back from EOF'
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126 print 'Read', len(list), 'more lines'
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127 print 'File length =', f.tell()
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128 if f.tell() != length:
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129 raise RuntimeError, 'bad length'
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130 f.close()
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131
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
parents:
diff changeset
132 if __name__ == '__main__':
0a60460e99f0 Two new generally useful modules: types defines names for all built-in types,
Guido van Rossum <guido@python.org>
parents:
diff changeset
133 test()