对于简单的一行代码(Python 3.0):

''.join(filter( lambda x: x in '0123456789abcdefghijklmnopqrstuvwxyz', the_string_you_want_stripped ))

对于Python < 3.0:

filter( lambda x: x in '0123456789abcdefghijklmnopqrstuvwxyz', the_string_you_want_stripped )

注意:如果需要，您可以将其他字符添加到允许字符列表中(例如:“0123456789 abcdefghijklmnopqrstuvwxyz。_”)。

sent = "".join(e for e in sent if e.isalpha())

作为这里其他一些答案的衍生，我提供了一种非常简单而灵活的方法来定义您想要限制字符串内容的一组字符。在这种情况下，我允许字母数字加破折号和下划线。只需添加或删除字符从我的PERMITTED_CHARS适合您的用例。

PERMITTED_CHARS = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-" 
someString = "".join(c for c in someString if c in PERMITTED_CHARS)

如果我理解正确，最简单的方法是使用正则表达式，因为它为您提供了很大的灵活性，但另一个简单的方法是使用循环以下是示例代码，我还计算了单词的出现并存储在字典中。

s = """An... essay is, generally, a piece of writing that gives the author's own 
argument — but the definition is vague, 
overlapping with those of a paper, an article, a pamphlet, and a short story. Essays 
have traditionally been 
sub-classified as formal and informal. Formal essays are characterized by "serious 
purpose, dignity, logical 
organization, length," whereas the informal essay is characterized by "the personal 
element (self-revelation, 
individual tastes and experiences, confidential manner), humor, graceful style, 
rambling structure, unconventionality 
or novelty of theme," etc.[1]"""

d = {}      # creating empty dic      
words = s.split() # spliting string and stroing in list
for word in words:
    new_word = ''
    for c in word:
        if c.isalnum(): # checking if indiviual chr is alphanumeric or not
            new_word = new_word + c
    print(new_word, end=' ')
    # if new_word not in d:
    #     d[new_word] = 1
    # else:
    #     d[new_word] = d[new_word] +1
print(d)

如果这个答案是有用的，请评价这个!

对于简单的一行代码(Python 3.0):

''.join(filter( lambda x: x in '0123456789abcdefghijklmnopqrstuvwxyz', the_string_you_want_stripped ))

对于Python < 3.0:

filter( lambda x: x in '0123456789abcdefghijklmnopqrstuvwxyz', the_string_you_want_stripped )

注意:如果需要，您可以将其他字符添加到允许字符列表中(例如:“0123456789 abcdefghijklmnopqrstuvwxyz。_”)。

我用perfplot(我的一个项目)检查了结果，发现对于短字符串，

"".join(filter(str.isalnum, s))

是最快的。对于长字符串(200+字符)

re.sub("[\W_]", "", s)

是最快的。

代码重现情节:

import perfplot
import random
import re
import string

pattern = re.compile("[\W_]+")


def setup(n):
    return "".join(random.choices(string.ascii_letters + string.digits, k=n))


def string_alphanum(s):
    return "".join(ch for ch in s if ch.isalnum())


def filter_str(s):
    return "".join(filter(str.isalnum, s))


def re_sub1(s):
    return re.sub("[\W_]", "", s)


def re_sub2(s):
    return re.sub("[\W_]+", "", s)


def re_sub3(s):
    return pattern.sub("", s)


b = perfplot.bench(
    setup=setup,
    kernels=[string_alphanum, filter_str, re_sub1, re_sub2, re_sub3],
    n_range=[2**k for k in range(10)],
)
b.save("out.png")
b.show()