如果你真的不喜欢到处使用try/except，请写一个helper函数:

def represents_int(s):
    try: 
        int(s)
    except ValueError:
        return False
    else:
        return True

>>> print(represents_int("+123"))
True
>>> print(represents_int("10.0"))
False

它将需要更多的代码来精确覆盖Python认为是整数的所有字符串。要我说，你就用蟒语吧。

正确的RegEx解决方案应该结合Greg Hewgill和Nowell的思想，但不使用全局变量。可以通过将属性附加到方法来实现这一点。另外，我知道在方法中导入是不受欢迎的，但我想要的是像http://peak.telecommunity.com/DevCenter/Importing#lazy-imports这样的“惰性模块”效果

edit:到目前为止，我最喜欢的技术是使用String对象的独占方法。

#!/usr/bin/env python

# Uses exclusively methods of the String object
def isInteger(i):
    i = str(i)
    return i=='0' or (i if i.find('..') > -1 else i.lstrip('-+').rstrip('0').rstrip('.')).isdigit()

# Uses re module for regex
def isIntegre(i):
    import re
    if not hasattr(isIntegre, '_re'):
        print("I compile only once. Remove this line when you are confident in that.")
        isIntegre._re = re.compile(r"[-+]?\d+(\.0*)?$")
    return isIntegre._re.match(str(i)) is not None

# When executed directly run Unit Tests
if __name__ == '__main__':
    for obj in [
                # integers
                0, 1, -1, 1.0, -1.0,
                '0', '0.','0.0', '1', '-1', '+1', '1.0', '-1.0', '+1.0',
                # non-integers
                1.1, -1.1, '1.1', '-1.1', '+1.1',
                '1.1.1', '1.1.0', '1.0.1', '1.0.0',
                '1.0.', '1..0', '1..',
                '0.0.', '0..0', '0..',
                'one', object(), (1,2,3), [1,2,3], {'one':'two'}
            ]:
        # Notice the integre uses 're' (intended to be humorous)
        integer = ('an integer' if isInteger(obj) else 'NOT an integer')
        integre = ('an integre' if isIntegre(obj) else 'NOT an integre')
        # Make strings look like strings in the output
        if isinstance(obj, str):
            obj = ("'%s'" % (obj,))
        print("%30s is %14s is %14s" % (obj, integer, integre))

对于那些不太喜欢冒险的同学，输出如下:

I compile only once. Remove this line when you are confident in that.
                             0 is     an integer is     an integre
                             1 is     an integer is     an integre
                            -1 is     an integer is     an integre
                           1.0 is     an integer is     an integre
                          -1.0 is     an integer is     an integre
                           '0' is     an integer is     an integre
                          '0.' is     an integer is     an integre
                         '0.0' is     an integer is     an integre
                           '1' is     an integer is     an integre
                          '-1' is     an integer is     an integre
                          '+1' is     an integer is     an integre
                         '1.0' is     an integer is     an integre
                        '-1.0' is     an integer is     an integre
                        '+1.0' is     an integer is     an integre
                           1.1 is NOT an integer is NOT an integre
                          -1.1 is NOT an integer is NOT an integre
                         '1.1' is NOT an integer is NOT an integre
                        '-1.1' is NOT an integer is NOT an integre
                        '+1.1' is NOT an integer is NOT an integre
                       '1.1.1' is NOT an integer is NOT an integre
                       '1.1.0' is NOT an integer is NOT an integre
                       '1.0.1' is NOT an integer is NOT an integre
                       '1.0.0' is NOT an integer is NOT an integre
                        '1.0.' is NOT an integer is NOT an integre
                        '1..0' is NOT an integer is NOT an integre
                         '1..' is NOT an integer is NOT an integre
                        '0.0.' is NOT an integer is NOT an integre
                        '0..0' is NOT an integer is NOT an integre
                         '0..' is NOT an integer is NOT an integre
                         'one' is NOT an integer is NOT an integre
<object object at 0x103b7d0a0> is NOT an integer is NOT an integre
                     (1, 2, 3) is NOT an integer is NOT an integre
                     [1, 2, 3] is NOT an integer is NOT an integre
                {'one': 'two'} is NOT an integer is NOT an integre

我有一种可能根本不使用int，除非字符串不代表数字，否则不应该引发异常

float(number)==float(number)//1

它应该适用于任何类型的字符串，float接受，正，负，工程符号…

如果你真的不喜欢到处使用try/except，请写一个helper函数:

def represents_int(s):
    try: 
        int(s)
    except ValueError:
        return False
    else:
        return True

>>> print(represents_int("+123"))
True
>>> print(represents_int("10.0"))
False

它将需要更多的代码来精确覆盖Python认为是整数的所有字符串。要我说，你就用蟒语吧。

先决条件:

我们谈论的是整数(不是小数/浮点数); 内置int()的行为是我们的标准(有时很奇怪:“-00”是它的正确输入)

简短的回答:

使用下面的代码。它简单，正确(虽然这个线程中的许多变体不是)，并且几乎是try/except和regex变体的两倍。

def is_int_str(string):
    return (
        string.startswith(('-', '+')) and string[1:].isdigit()
    ) or string.isdigit()

TL;博士答:

我已经测试了3个主要变体(1)try/except， (2) re.match()和(3)字符串操作(见上文)。第三个变体比try/except和re.match()快两倍。顺便说一句:regex变体是最慢的!请参见下面的测试脚本。

import re
import time


def test(func, test_suite):
    for test_case in test_suite:
        actual_result = func(*test_case[0])
        expected_result = test_case[1]
        assert (
            actual_result == expected_result
        ), f'Expected: {expected_result} but actual: {actual_result}'


def perf(func, test_suite):
    start = time.time()

    for _ in range(0, 1_000_000):
        test(func, test_suite)

    return time.time() - start


def is_int_str_1(string):
    try:
        int(string)
        return True
    except ValueError:
        return False


def is_int_str_2(string):
    return re.match(r'^[\-+]?\d+$', string) is not None


def is_int_str_3(string):
    return (
        string.startswith(('-', '+')) and string[1:].isdigit()
    ) or string.isdigit()


# Behavior of built-in int() function is a standard for the following tests
test_suite = [
    [['1'], True],  # func('1') -> True
    [['-1'], True],
    [['+1'], True],
    [['--1'], False],
    [['++1'], False],
    [['001'], True],  # because int() can read it
    [['-00'], True],  # because of quite strange behavior of int()
    [['-'], False],
    [['abracadabra'], False],
    [['57938759283475928347592347598357098458405834957984755200000000'], True],
]

time_span_1 = perf(is_int_str_1, test_suite)
time_span_2 = perf(is_int_str_2, test_suite)
time_span_3 = perf(is_int_str_3, test_suite)

print(f'{is_int_str_1.__name__}: {time_span_1} seconds')
print(f'{is_int_str_2.__name__}: {time_span_2} seconds')
print(f'{is_int_str_3.__name__}: {time_span_3} seconds')

输出是:

is_int_str_1: 4.314162969589233 seconds
is_int_str_2: 5.7216269969940186 seconds
is_int_str_3: 2.5828163623809814 seconds

我的建议如下:

import ast

def is_int(s):
    return isinstance(ast.literal_eval(s), int)

从文档中可以看出:

安全地计算表达式节点或包含Python文字或容器显示的字符串。提供的字符串或节点只能由以下Python文字结构组成:字符串、字节、数字、元组、列表、字典、集、布尔值和None。

我应该指出，当对任何不构成Python文字的内容调用时，这将引发ValueError异常。因为这个问题要求一个没有try/except的解决方案，我有一个Kobayashi-Maru类型的解决方案:

from ast import literal_eval
from contextlib import suppress

def is_int(s):
    with suppress(ValueError):
        return isinstance(literal_eval(s), int)
    return False

¯\_(五)_/¯