How to subtract known substring from larger string

Question

I have been trying to deconstruct a string in the following way:

Full String

str = 'Hello world I am Bob'

Substring 1

sub_str1 = 'Hello world'

Substring 2

sub_str2 = 'world I'

Desired Outcome:

1. Using substring 1:

   Apply some regular expression to get:

   answer = ' I am Bob'
   

2. Using substring 2:

   answer = 'Hello  I am Bob'
   

I have tried a number of different approaches with regular expression, but I have just started using them and am not at all proficient.

Solution

You can replace parts of a string with some other string.

"Substracting" would be replacing a substring with an empty string:

>>> 'Hello world I am Bob'.replace('Hello world', '')
' I am Bob'

Comments

[aacealo]

Thanks. I'm just curious to know if you think this is faster than a regex? I'd use timeit to test, but I can't figure out a regular expression that will accomplish the same thing.

[Geoff]

s/Hello world// is the replacement regex

[zvone]

@aacealo Regex to find "Hello world" is "Hello world". This sam thing with regex would be re.sub('Hello world', '', 'Hello world I am Bob'). I did not time it, but I am sure regex is much slower. The only reason to use regex is if you want to do something more complex, e.g. replace the first two words whatever they are: re.sub(r'^ *\w+ +\w+ +', '', 'Hello world I am Bob')

[aacealo]

Okay, I think I'll just go with your approach. It makes sense, and it's simpler than trying to learn regular expression.