Strip removing more characters than expected

Question

Can anyone explain what\'s going on here:

s = \'REFPROP-MIX:METHANOL&WATER\'
s.lstrip(\'REFPROP-MIX\')   # this returns \':METHANOL&WATER\' as expect         


        

Answer 1

str.lstrip removes all the characters in its argument from the string, starting at the left. Since all the characters in the left prefix "REFPROP-MIX:ME" are in the argument "REFPROP-MIX:", all those characters are removed. Likewise:

>>> s = 'abcadef'
>>> s.lstrip('abc')
'def'
>>> s.lstrip('cba')
'def'
>>> s.lstrip('bacabacabacabaca')
'def'

str.lstrip does not remove whole strings (of length greater than 1) from the left. If you want to do that, use a regular expression with an anchor ^ at the beginning:

>>> import re
>>> s = 'REFPROP-MIX:METHANOL&WATER'
>>> re.sub(r'^REFPROP-MIX:', '', s)
'METHANOL&WATER'

Answer 2

The method mentioned by @PadraicCunningham is a good workaround for the particular problem as stated.

Just split by the separating character and select the last value:

s = 'REFPROP-MIX:METHANOL&WATER'
res = s.split(':', 1)[-1]  # 'METHANOL&WATER'