I have a string, s = 'sdfjoiweng%@$foo$fsoifjoi', and I would like to replace 'foo' with 'bar'.
I tried re.sub(r'\bfoo\b', 'bar', s) and re.sub(r'[foo]', 'bar', s), but it doesn't do anything. What am I doing wrong?
4 Answers
You can replace it directly:
>>> import re
>>> s = 'sdfjoiweng%@$foo$fsoifjoi'
>>> print(re.sub('foo','bar',s))
sdfjoiweng%@$bar$fsoifjoi
It will also work for more occurrences of foo like below:
>>> s = 'sdfjoiweng%@$foo$fsoifoojoi'
>>> print(re.sub('foo','bar',s))
sdfjoiweng%@$bar$fsoibarjoi
If you want to replace only the 1st occurrence of foo and not all the foo occurrences in the string then alecxe's answer does exactly that.
3 Comments
alecxe
I'm not sure if OP is okay with
foo being replaced in parts of words, like in your second case.alecxe
Plus, why
re.sub() then and not replace()?
coder
@alecxe, I totally agree with you that
replace also could be used instead - as it is considered more readable, but the OP asked specifically for regex. As for the first comment the OP should specify if he wants foo being replaced in parts of words.
re.sub(r'\bfoo\b', 'bar', s)
Here, the \b defines the word boundaries - positions between a word character (\w) and a non-word character - exactly what you have matching for foo inside the sdfjoiweng%@$foo$fsoifjoi string. Works for me:
In [1]: import re
In [2]: s = 'sdfjoiweng%@$foo$fsoifjoi'
In [3]: re.sub(r'\bfoo\b', 'bar', s)
Out[3]: 'sdfjoiweng%@$bar$fsoifjoi'
1 Comment
Geeocode
My only problem with \b that it doesn't work when spaces are the bounderies around the word. Do you have some solution on it? e.g.
s = 'sdfjoiweng%@$foo foo $fsoifjoi' won't workYou can use replace function directly instead of using regex.
>>> s = 'sdfjoiweng%@$foo$fsoifjoifoo'
>>>
>>> s.replace("foo","bar")
'sdfjoiweng%@$bar$fsoifjoibar'
>>>
>>>
Comments
To further add to the above, the code below shows you how to replace multiple words at once! I've used this to replace 165,000 words in 1 step!!
Note \b means no sub string matching..must be a whole word..if you remove it then it will make sub-string match.
import re
s = 'thisis a test'
re.sub('\bthis\b|test','',s)
This gives:
'thisis a '
8 Comments
Geeocode
My only problem with \b that it doesn't work when spaces are the bounderies around the word. So
e.g: re.sub('\bthis\b|test', '', 'thisis this a test') results in thisis this a Do you have some solution on it?Geeocode
I want to get
thisis a as a result. So I want to replace the 2nd this in the string.Geeocode
More understandable example:
thisis this this a test to thisis that that a that
Chadee Fouad
Oh great thanks :-)...I would have suggested a 2 step approach to fix the problem but seems you found a solution already...can you please post your solution so that I'd learn from it too? :-)
Geeocode
This is my solution:
re.sub("\bthis\b|test", "Q", re.sub(" this ", " Q ", "thisis this is a test")) It is a nested van, as I talked about a nested solution, but of course it can be a two liner as well (as I actually did it). The result: thisis Q is a Q |
print re.sub(r'\bfoo\b', 'bar', s)is correctly giving mesdfjoiweng%@$bar$fsoifjoisto be modified in place? Strings in Python are immutable. The new modified string will be returned byre.sub.