将 isalpha() 和 isspace() 合并为 1 个语句

Question

I am looking for a function that combines the methods isalpha() and isspace() into a single method. I want to check if a given string only contains letters and/or spaces, for example:

"This is text".isalpha_or_space()
# True

However, with the 2 methods, I get:

"This is text".isalpha() or "This is text".isspace()
# False

as the string is not only alpha nor space.

---

Of course, I could iterate over every character and check it for space or alpha.

I could also compare the string with ("abcdefghijklmnopqrstuvwxyz" + " ")

However, both of these approaches don't seem very pythonic to me - convince me otherwise.

Answer 1

The most Pythonic will be to use a def for this:

def isalpha_or_space(self):
    if self == "":
        return False
    for char in self:
        if not (char.isalpha() or char.isspace()):
            return False
    return True

It is not easy to contribute this as a method on str , since Python does not encourage the monkeypatching of built-in types. My recommendation is just to leave this as a module level function.

Nonetheless, it is still possible to mimic the interface of a method, since most namespaces in Python are writable if you know where to find them. The suggestion below is not Pythonic, and relies on implementation detail.

>>> import gc
>>> def monkeypatch(type_, func): 
...     gc.get_referents(type_.__dict__)[0][func.__name__] = func 
...
>>> monkeypatch(str, isalpha_or_space)
>>> "hello world".isalpha_or_space()
True

Answer 2

Use a regular expression (regex) :

>>> import re
>>> result = re.match('[a-zA-Z\s]+$', "This is text")
>>> bool(result)
True

Breakdown:

• re - Python's regex module
• [a-zA-Z\\s] - Any letter or whitespace
• + - One or more of the previous item
• $ - End of string

---

The above works with ASCII letters. For the full Unicode range on Python 3, unfortunately the regex is a bit complicated:

>>> result = re.match('([^\W\d_]|\s)+$', 'un café')

Breakdown:

• (x|y) - x or y
• [^\\W\\d_] - Any word character except a number or an underscore

From Mark Tolonen 's answer on How to match all unicode alphabetic characters and spaces in a regex?

Answer 3

您可以使用以下解决方案：

s != '' and all(c.isalpha() or c.isspace() for c in s)