Hat symbol inside sets in Python regular expressions
As you know, the hat inside [ ] negates when written at the beginning of brackets. So, it is a special symbol inside these brackets. To get the hat as a symbol, you need to either escape it or remove it from the first place.
Example
In the following example, the search pattern is: the first character is everything except 'd', then the two letters 'x':
txt = 'axx bxx ^xx dxx'
res = re.sub('[^d]xx', '!', txt)
print(res)
As a result, the following will be written to the variable:
'! ! ! dxx'
Example
Now the search template is: the first character is 'd' or '^', then two letters 'x':
txt = 'axx bxx ^xx dxx'
res = re.sub('[d^]xx', '!', txt)
print(res)
As a result, the following will be written to the variable:
'axx bxx ! !'
Example
You don't have to remove the header from the first place, but simply escape it with a backslash, and it will begin to denote itself:
txt = 'axx bxx ^xx dxx'
res = re.sub('[\^d]xx', '!', txt)
print(res)
As a result, the following will be written to the variable:
'axx bxx ! !'
Practical tasks
Given a string:
txt = '^xx axx ^zz bkk @ss'
Write a regular expression that will find lines according to the pattern: a hat or a dog, then two Latin letters.
Given a string:
txt = '^xx axx ^zz bkk @ss'
Write a regular expression that will find lines according to the pattern: NOT a hat and not a dog, and then two Latin letters.
Given a string:
txt = '^xx axx ^zz bkk'
Write a regular expression that will find lines according to the pattern: not a hat and not a space, and then two Latin letters.
