Find and replace in a file with regular expression

[TOXiC]

Hi everyone,
First I say that I serched and tryed everything but I cannot figure
out how I can do it.
I want to open a a file (not necessary a txt) and find and replace a
string.
I can do it with:

import fileinput, string, sys
fileQuery = "Text.txt"
sourceText = '''SOURCE'''
replaceText = '''REPLACE'''
def replace(fileNam e, sourceText, replaceText):

file = open(fileName, "r")
text = file.read() #Reads the file and assigns the value to a
variable
file.close() #Closes the file (read session)
file = open(fileName, "w")
file.write(text .replace(source Text, replaceText))
file.close() #Closes the file (write session)
print "All went well, the modifications are done"

replacemachine( fileQuery, sourceText, replaceText)

Now all went ok but I'm wondering if it's possible to replace text if /
sourceText/ match a regex.
Help me please!
Thx in advance

[Matimus]

The re module is used for regular expressions. Something like this
should work (untested):

import fileinput, string, sys, re

fileQuery = "Text.txt"
sourceText = '''SOURCE'''
replaceText = '''REPLACE'''

def replace(fileNam e, sourceText, replaceText):
file = open(fileName, "r")
text = file.read() #Reads the file and assigns the value to a
variable
file.close() #Closes the file (read session)

file = open(fileName, "w")
file.write(re.s ub(sourceText, replaceText,tex t))
file.close() #Closes the file (write session)

print "All went well, the modifications are done"

replacemachine( fileQuery, sourceText, replaceText)

[Wolfgang Grafen]

Just in case you didn't think about it there is a plain replace method for strings

How to quick-search this method with 'dir'

>>dir("")

['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__ge__', '__getattribute __', '__getitem__', '__getnewargs__ ', '__getslice__', '__gt__', '__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__' ,
'__repr__', '__rmod__', '__rmul__', '__setattr__', '__str__', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith', 'expandtabs', 'find', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'replace', 'rfind', 'rindex',
'rjust', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']

>>help("".repla ce)

Help on built-in function replace:

replace(...)
S.replace (old, new[, maxsplit]) -string

Return a copy of string S with all occurrences of substring
old replaced by new. If the optional argument maxsplit is
given, only the first maxsplit occurrences are replaced.

and now how to apply it:
new_text = open(fileName). read().replace( "SOURCE", "REPLACE")

which is the preferred method for a simple task like this.

TOXiC wrote:

Hi everyone,
First I say that I serched and tryed everything but I cannot figure
out how I can do it.
I want to open a a file (not necessary a txt) and find and replace a
string.
I can do it with:

import fileinput, string, sys
fileQuery = "Text.txt"
sourceText = '''SOURCE'''
replaceText = '''REPLACE'''
def replace(fileNam e, sourceText, replaceText):

Now how to solve it with a simple regular expression:

>>import re
re_replace = re.compile("SOU RCE").sub

txt = " SOURCE SOURCE \n SOURCE "

print re_replace("REP LACE", txt)

' REPLACE REPLACE \n REPLACE '

>>new_text = re_replace("REP LACE", open(fileName). read())

A regular expression for this task is kind of overkill. Mastering
regular expression is the efford very worth.

Wolfgang Grafen

[Frederic Rentsch]

TOXiC wrote:

Hi everyone,
First I say that I serched and tryed everything but I cannot figure
out how I can do it.
I want to open a a file (not necessary a txt) and find and replace a
string.
I can do it with:

import fileinput, string, sys
fileQuery = "Text.txt"
sourceText = '''SOURCE'''
replaceText = '''REPLACE'''
def replace(fileNam e, sourceText, replaceText):

file = open(fileName, "r")
text = file.read() #Reads the file and assigns the value to a
variable
file.close() #Closes the file (read session)
file = open(fileName, "w")
file.write(text .replace(source Text, replaceText))
file.close() #Closes the file (write session)
print "All went well, the modifications are done"

replacemachine( fileQuery, sourceText, replaceText)

Now all went ok but I'm wondering if it's possible to replace text if /
sourceText/ match a regex.
Help me please!
Thx in advance

Try this:

>>import SE # from http://cheeseshop.python.org/pypi/SE/2.3

>>replacement s = 'SOURCE=REPLACE "another source=another replace"

~[0-9]+~=>>int<< ~[0-9]+\\.[0-9]+~=>>float<< ~'
# Define as many replacements as you like. Identify regexes placing
them between '~'

>>Stream_Edit or = SE.SE (replacements)

>>Stream_Edit or (input_file, output_file)

That's it.
PS 1: Your Stream_Editor accepts strings as well as file names and then
returns a string by default. This is a great help for developing
substitution sets interactively.

>>print Stream_Editor ('''

If it works, this SOURCE should read REPLACE
and another source should become another replace
and this 123456789 should become >>int<<
and this 12345.6789 is a float and so should read >>float<<.''' )

If it works, this REPLACE should read REPLACE
and another replace should become another replace
and this >>int<< should become >>int<<
and this >>float<< is a float and so should read >>float<<.

PS 2: It is convenient to keep large and frequently used substitution
sets in text files. The SE constructor accepts a file name instead of
the replacements string:

>>Stream_Edto r = SE.SE ('path/replacement_def initions_file')

Regards

Frederic