去除比预期更多的字符

问题描述

谁能解释一下这里发生了什么:

s = 'REFPROP-MIX:METHANOL&WATER's.lstrip('REFPROP-MIX') # 这会按预期返回 ':METHANOL&WATER's.lstrip('REFPROP-MIX:') # 返回 'THANOL&WATER'

那个我"怎么了?冒号是 lstrip 的特殊字符吗?这尤其令人困惑，因为它按预期工作:

s = 'abc-def:ghi's.lstrip('abc-def') # 返回 ':ghi's.lstrip('abd-def:') # 返回 'ghi'

解决方案

str.lstrip 从字符串中删除其参数中的所有字符，从左边开始.由于左前缀REFPROP-MIX:ME"中的所有字符都在参数REFPROP-MIX:"中，所有这些字符都被删除.同样:

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

str.lstrip 不会从左边删除整个字符串(长度大于 1).如果要这样做，请使用以 ^ 开头的正则表达式:

>>>进口重新>>>s = 'REFPROP-MIX:甲醇和水'>>>re.sub(r'^REFPROP-MIX:', '', s)'甲醇和水'

Can anyone explain what's going on here:

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

What happened to that 'ME'? Is a colon a special character for lstrip? This is particularly confusing because this works as expected:

s = 'abc-def:ghi'
s.lstrip('abc-def')   # returns ':ghi'
s.lstrip('abd-def:')  # returns 'ghi'

解决方案

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'

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