Search For Strings In Python

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 strin

Solution 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.

Solution 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].

Solution 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.