问题
How could I search for a string in a text and add another string after it like the following:
I want to search for example "John 3 2 G" in a text if it is there I want to add strings after it
I met John 3 2 G yesterday and..
after run the program
I met John 3 2 G and his brother yesterday and..
to be known that the numbers are not fixed, they are numbers but could be changed
I used re.sub but in this case when the numbers are changing how could I do it ?
My attempt:
re.sub("John","John and his brother",text)
回答1:
You can use regular expression pattern matching to tell Python to Match "'John', followed by a space, followed by a digit, followed by a space, followed by a digit, followed by a capital letter".
>>> re.sub(r"John\s(\d\s\d\s[A-Z])", r"John \1 and his brother", a)
'I met John 3 2 G and his brother yesterday'
\s = whitespace
\d = digit
[A-Z] = Captial letter between A and Z.
The parenthesis around \d\s\d\s[A-Z] tells Python to "capture" that part of the matched pattern, allowing us to access it in the replacement string using \1.
回答2:
Since you know that they'll be numbers but you don't know for sure what the numbers will be, you could use
text = re.sub(r'(\w+ \d+ \d+ \w+)',r'\1 and his brother',text)
That should replace "I met <word> <number> <number> <word> yesterday and..." where John and G can be anything so long as they appear in that order with two numbers between.
If you need it to replace specifically a single capital letter in the fourth spot, you can change the \w+ to [A-Z].
回答3:
You could try the below regex which uses positive lookahead,
>>> import re
>>> str = 'I met John 3 2 G yesterday and..'
>>> m = re.sub(r'(John.*)(?=yesterday)', r'\1and his brother ', str)
>>> m
'I met John 3 2 G and his brother yesterday and..'
Explanation:
(John.*)(?=yesterday)Matches all the characters which are followed by the string John(including John) upto the string yesterday and stored it into a group.In the replacement part we again call the stored group through backreference.
来源：https://stackoverflow.com/questions/24392346/search-for-strings-in-python