Mercurial > cpython-lru_cache-weakref

annotate Lib/regsub.py @ 5817:48b94de85bf3 legacy-trunk

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Extensive changes by AMK.
author Guido van Rossum <guido@python.org>
date Thu, 17 Jul 1997 16:29:42 +0000
parents 0bf7394dba22
children 6f4146846337
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1 # Regular expression subroutines:
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2 # sub(pat, repl, str): replace first occurrence of pattern in string
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3 # gsub(pat, repl, str): replace all occurrences of pattern in string
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4 # split(str, pat, maxsplit): split string using pattern as delimiter
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5 # splitx(str, pat, maxsplit): split string using pattern as delimiter plus
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6 # return delimiters
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7
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8
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9 import regex
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10
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11
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12 # Replace first occurrence of pattern pat in string str by replacement
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13 # repl. If the pattern isn't found, the string is returned unchanged.
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14 # The replacement may contain references \digit to subpatterns and
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15 # escaped backslashes. The pattern may be a string or an already
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16 # compiled pattern.
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17
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18 def sub(pat, repl, str):
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19 prog = compile(pat)
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20 if prog.search(str) >= 0:
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21 regs = prog.regs
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22 a, b = regs[0]
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23 str = str[:a] + expand(repl, regs, str) + str[b:]
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24 return str
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25
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26
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27 # Replace all (non-overlapping) occurrences of pattern pat in string
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28 # str by replacement repl. The same rules as for sub() apply.
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29 # Empty matches for the pattern are replaced only when not adjacent to
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30 # a previous match, so e.g. gsub('', '-', 'abc') returns '-a-b-c-'.
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31
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32 def gsub(pat, repl, str):
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33 prog = compile(pat)
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34 new = ''
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35 start = 0
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36 first = 1
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37 while prog.search(str, start) >= 0:
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38 regs = prog.regs
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39 a, b = regs[0]
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40 if a == b == start and not first:
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41 if start >= len(str) or prog.search(str, start+1) < 0:
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42 break
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43 regs = prog.regs
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44 a, b = regs[0]
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45 new = new + str[start:a] + expand(repl, regs, str)
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46 start = b
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47 first = 0
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48 new = new + str[start:]
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49 return new
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50
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51
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52 # Split string str in fields separated by delimiters matching pattern
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53 # pat. Only non-empty matches for the pattern are considered, so e.g.
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54 # split('abc', '') returns ['abc'].
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55 # The optional 3rd argument sets the number of splits that are performed.
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56
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57 def split(str, pat, maxsplit = 0):
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58 return intsplit(str, pat, maxsplit, 0)
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59
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60 # Split string str in fields separated by delimiters matching pattern
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61 # pat. Only non-empty matches for the pattern are considered, so e.g.
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62 # split('abc', '') returns ['abc']. The delimiters are also included
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63 # in the list.
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64 # The optional 3rd argument sets the number of splits that are performed.
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65
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66
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67 def splitx(str, pat, maxsplit = 0):
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68 return intsplit(str, pat, maxsplit, 1)
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69
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70 # Internal function used to implement split() and splitx().
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71
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72 def intsplit(str, pat, maxsplit, retain):
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73 prog = compile(pat)
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74 res = []
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75 start = next = 0
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76 splitcount = 0
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77 while prog.search(str, next) >= 0:
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78 regs = prog.regs
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79 a, b = regs[0]
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80 if a == b:
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81 next = next + 1
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82 if next >= len(str):
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83 break
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84 else:
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85 res.append(str[start:a])
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86 if retain:
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87 res.append(str[a:b])
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88 start = next = b
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89 splitcount = splitcount + 1
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90 if (maxsplit and (splitcount >= maxsplit)):
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91 break
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92 res.append(str[start:])
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93 return res
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94
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95
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96 # Capitalize words split using a pattern
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97
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98 def capwords(str, pat='[^a-zA-Z0-9_]+'):
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99 import string
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100 words = splitx(str, pat)
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101 for i in range(0, len(words), 2):
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102 words[i] = string.capitalize(words[i])
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103 return string.joinfields(words, "")
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104
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105
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106 # Internal subroutines:
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107 # compile(pat): compile a pattern, caching already compiled patterns
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108 # expand(repl, regs, str): expand \digit escapes in replacement string
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109
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110
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111 # Manage a cache of compiled regular expressions.
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112 #
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113 # If the pattern is a string a compiled version of it is returned. If
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114 # the pattern has been used before we return an already compiled
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115 # version from the cache; otherwise we compile it now and save the
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116 # compiled version in the cache, along with the syntax it was compiled
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117 # with. Instead of a string, a compiled regular expression can also
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118 # be passed.
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119
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120 cache = {}
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121
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122 def compile(pat):
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123 if type(pat) <> type(''):
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124 return pat # Assume it is a compiled regex
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125 key = (pat, regex.get_syntax())
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126 if cache.has_key(key):
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127 prog = cache[key] # Get it from the cache
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128 else:
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129 prog = cache[key] = regex.compile(pat)
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130 return prog
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131
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132
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133 def clear_cache():
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134 global cache
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135 cache = {}
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136
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137
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138 # Expand \digit in the replacement.
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139 # Each occurrence of \digit is replaced by the substring of str
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140 # indicated by regs[digit]. To include a literal \ in the
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141 # replacement, double it; other \ escapes are left unchanged (i.e.
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142 # the \ and the following character are both copied).
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143
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144 def expand(repl, regs, str):
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145 if '\\' not in repl:
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146 return repl
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147 new = ''
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148 i = 0
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149 ord0 = ord('0')
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150 while i < len(repl):
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151 c = repl[i]; i = i+1
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152 if c <> '\\' or i >= len(repl):
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153 new = new + c
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154 else:
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155 c = repl[i]; i = i+1
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156 if '0' <= c <= '9':
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157 a, b = regs[ord(c)-ord0]
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158 new = new + str[a:b]
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159 elif c == '\\':
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160 new = new + c
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161 else:
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162 new = new + '\\' + c
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163 return new
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164
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165
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166 # Test program, reads sequences "pat repl str" from stdin.
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167 # Optional argument specifies pattern used to split lines.
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168
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169 def test():
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170 import sys
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171 if sys.argv[1:]:
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172 delpat = sys.argv[1]
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173 else:
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174 delpat = '[ \t\n]+'
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175 while 1:
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176 if sys.stdin.isatty(): sys.stderr.write('--> ')
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177 line = sys.stdin.readline()
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178 if not line: break
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179 if line[-1] == '\n': line = line[:-1]
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180 fields = split(line, delpat)
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181 if len(fields) <> 3:
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182 print 'Sorry, not three fields'
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183 print 'split:', `fields`
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184 continue
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185 [pat, repl, str] = split(line, delpat)
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186 print 'sub :', `sub(pat, repl, str)`
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187 print 'gsub:', `gsub(pat, repl, str)`