python 检查有效的电子邮件

Question

Python Central 发布了此 simple script 2016 年 12 月 29 日检查电子邮件格式是否正确。

import re

def isValidEmail(email):
    if len(email) > 7:
        if re.match("^.+@([?)[a-zA-Z0-9-.]+.([a-zA-Z]{2,3}|[0-9]{1,3})(]?)$", email) != None:
            return True
        return False

if isValidEmail("<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="55382c7b3038343c39153238343c397b363a38" rel="noreferrer noopener nofollow">[email protected]</a>") == True:
    print("This is a valid email address")
else:
    print("This is not a valid email address")

在尝试时，python 3 返回了以下错误消息:

Traceback (most recent call last):
  File "~/isValidEmail.py", line 11, in <module>
    if isValidEmail("<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="f89581d69d95999194b89f95999194d69b9795" rel="noreferrer noopener nofollow">[email protected]</a>") == True:
  File "~/isValidEmail.py", line 7, in isValidEmail
    if re.match("^.+@([?)[a-zA-Z0-9-.]+.([a-zA-Z]{2,3}|[0-9]{1,3})(]?)$", email) != None:
  File "/usr/lib/python3.5/re.py", line 163, in match
    return _compile(pattern, flags).match(string)
  File "/usr/lib/python3.5/re.py", line 293, in _compile
    p = sre_compile.compile(pattern, flags)
  File "/usr/lib/python3.5/sre_compile.py", line 536, in compile
    p = sre_parse.parse(p, flags)
  File "/usr/lib/python3.5/sre_parse.py", line 829, in parse
    p = _parse_sub(source, pattern, 0)
  File "/usr/lib/python3.5/sre_parse.py", line 437, in _parse_sub
    itemsappend(_parse(source, state))
  File "/usr/lib/python3.5/sre_parse.py", line 781, in _parse
    source.tell() - start)
sre_constants.error: missing ), unterminated subpattern at position 4

如何修复此错误？

Answer 1

右括号 ) 包含在方括号内，因为它之前的方括号未正确转义。

^.+@([?)[a-zA-Z0-9-.]+.
     ^
     v
^.+@(\[?)[a-zA-Z0-9-.]+.

示例:

In[2]: import re
  ...: 
  ...: 
  ...: def is_valid_email(email):
  ...:     if len(email) > 7:
  ...:         return bool(re.match(
  ...:             "^.+@(\[?)[a-zA-Z0-9-.]+.([a-zA-Z]{2,3}|[0-9]{1,3})(]?)$", email))
  ...: 
In[3]: is_valid_email("<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="89e4f0a7ece4e8e0e5c9eee4e8e0e5a7eae6e4" rel="noreferrer noopener nofollow">[email protected]</a>")
Out[3]: True