python - str.lstrip() 意外行为

Question

我正在做一个 scrapy 项目并试图解析我的配置

字符串是 attr_title 我必须去掉 'attr_' 并得到 title。我使用了 lstrip('attr_')，但得到了意想不到的结果。我知道 lstrip 计算组合并删除它们，但很难理解它。

In [17]: "attr.title".lstrip('attr.')
Out[17]: 'itle'

PS:我知道有多种提取字符串的解决方案，我有兴趣了解这一点。

Answer 1

lstrip 迭代结果字符串，直到没有更多的组合匹配最左边的字符集

下面是一个小插图。

In [1]: "attr.title".lstrip('attr.')
Out[1]: 'itle'  # Flow --> "attr." --> "t" --> Next char is 'i' which does not match any combination hence, iteration stops & end result ('itle') is returned

In [2]: "attr.tritle".lstrip('attr.')
Out[2]: 'itle' # "attr." --> "t" --> "r" --> Next char is 'i' which does not match any combination hence, iteration stops & end result ('itle') is returned

In [5]: "attr.itratitle".lstrip('attr.')
Out[5]: 'itratitle' # "attr." --> Next char is 'i' which does not match any combination hence, iteration stops & end result ('itratitle') is returned