如何在Python中的一定数量的单词后剥离字符串

Question

I have a paragraph "Lorem ipsum foo bar foobar stuff etc"
In python, how might I strip this string after a certain amount of words say in this case 4?

Answer 1

If you only want them separated by spaces then:

>>>s = "Lorem ipsum foo bar foobar stuff etc"
>>>o = ' '.join(s.split(' ')[:4])
"Lorem ipsum foo bar"

should do the trick.

This is very naive, if you need something fancier then regex are the way to go. By something fancier I'm referring to more delimiters than spaces, grammar punctuation, etc.

For example:

>>>import re
>>>s = "Lorem ipsum foo bar foobar stuff etc"
>>>l = re.split('[\n \r \s \t]', s)
['Lorem', 'ipsum', 'foo', 'bar']
>>>str.join(' ', l)
"Lorem ipsum foo bar"

Hope this helps!

Answer 2

@PauloBlu's answer would work in most cases, except when your paragraph contains words with uneven whitespaces. Regex can work wonder in such cases

>>> s = "Lorem ipsum\tfoo    bar foobar stuff etc"
>>> ''.join(re.findall("^[^\s]+|\s+[^\s]+", s)[:4])
'Lorem ipsum\tfoo    bar'

whereas using str.split + str.join may not provide you the right result

>>> ' '.join(s.split(' ')[:4])
'Lorem ipsum\tfoo  '

Answer 3

I have two solutions.

The first uses more memory:

s = "Lorem ipsum foo bar foobar stuff etc"
print ' '.join(s.split(" ")[:4])

The second may be slower:

s = "Lorem ipsum foo bar foobar stuff etc"
start = 0
for i in range(4): # number of words
    start = s.find(" ", start+1)
print s[:start]

Answer 4

In addition to the other answers you could also use this form. It's not so different, but it works:

s = "Lorem ipsum foo bar foobar stuff etc"

print ' '.join(s.split(' ', 4)[:-1]) 
# the maxsplit arg of split('4' here) could be set to any number 'n'

"Lorem ipsum foo bar"