What's the most pythonic way to apply a functi

问题:

Suppose I have a function

def f(a):
  return a[::-1]

I want to apply the function f to every word on a string. If the string consists only of spaces, I can do

>>> s = '   this  is a banana   '
>>> ' '.join(map(f, s.split(' ')))
'   siht  si a ananab   '

But how can I do this when the string consists of multiple types of white spaces? (e.g., \t and \n)

For example, I want to change

'\t  \t this  is a\tbanana   \n'

to

'\t  \t siht  si a\tananab   \n'

回答1:

Use a regular expression, the re.sub() function accepts a function to do the substitutions. Match non-whitespace instead:

re.sub(r'[^\s]+', lambda m: f(m.group(0)), s)

The function is passed a match object; using .group(0) you can extract the matched text to pass it to your function. The return value is used to replace the original matched text in the output string.

Demo:

>>> import re
>>> def f(a):
...   return a[::-1]
...
>>> s = '\t  \t this  is a\tbanana   \n'
>>> re.sub(r'[^\s]+', lambda m: f(m.group(0)), s)
'\t  \t siht  si a\tananab   \n'

回答2:

Use regular expressions, where you can easily get whole words and also whole chunks of continuous whitespace.