下面是一个解析时不会产生错误的函数。它处理明显的情况，失败时返回None(在CPython上默认处理最多2000个'-/+'符号!):

#!/usr/bin/env python

def get_int(number):
    splits = number.split('.')
    if len(splits) > 2:
        # too many splits
        return None
    if len(splits) == 2 and splits[1]:
        # handle decimal part recursively :-)
        if get_int(splits[1]) != 0:
            return None

    int_part = splits[0].lstrip("+")
    if int_part.startswith('-'):
        # handle minus sign recursively :-)
        return get_int(int_part[1:]) * -1
    # successful 'and' returns last truth-y value (cast is always valid)
    return int_part.isdigit() and int(int_part)

一些测试:

tests = ["0", "0.0", "0.1", "1", "1.1", "1.0", "-1", "-1.1", "-1.0", "-0", "--0", "---3", '.3', '--3.', "+13", "+-1.00", "--+123", "-0.000"]

for t in tests:
    print "get_int(%s) = %s" % (t, get_int(str(t)))

结果:

get_int(0) = 0
get_int(0.0) = 0
get_int(0.1) = None
get_int(1) = 1
get_int(1.1) = None
get_int(1.0) = 1
get_int(-1) = -1
get_int(-1.1) = None
get_int(-1.0) = -1
get_int(-0) = 0
get_int(--0) = 0
get_int(---3) = -3
get_int(.3) = None
get_int(--3.) = 3
get_int(+13) = 13
get_int(+-1.00) = -1
get_int(--+123) = 123
get_int(-0.000) = 0

如有需要，可使用:

def int_predicate(number):
     return get_int(number) is not None

对于正整数，可以使用.isdigit:

>>> '16'.isdigit()
True

但它对负整数不起作用。假设您可以尝试以下方法:

>>> s = '-17'
>>> s.startswith('-') and s[1:].isdigit()
True

它不适用于'16.0'格式，在这个意义上，'16.0'格式类似于int类型强制转换。

编辑:

def check_int(s):
    if s[0] in ('-', '+'):
        return s[1:].isdigit()
    return s.isdigit()

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…

我猜这个问题与速度有关，因为try/except有一个时间惩罚:

测试数据

首先，我创建了一个包含200个字符串、100个失败字符串和100个数字字符串的列表。

from random import shuffle
numbers = [u'+1'] * 100
nonumbers = [u'1abc'] * 100
testlist = numbers + nonumbers
shuffle(testlist)
testlist = np.array(testlist)

numpy解决方案(仅适用于数组和unicode)

Np.core.defchararray.isnumeric也可以用于unicode字符串，但它返回一个数组。所以，如果你必须做成千上万的转换，并且有丢失的数据或非数值数据，这是一个很好的解决方案。

import numpy as np
%timeit np.core.defchararray.isnumeric(testlist)
10000 loops, best of 3: 27.9 µs per loop # 200 numbers per loop

试/除了

def check_num(s):
  try:
    int(s)
    return True
  except:
    return False

def check_list(l):
  return [check_num(e) for e in l]

%timeit check_list(testlist)
1000 loops, best of 3: 217 µs per loop # 200 numbers per loop

numpy解决方案似乎更快。

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

You know, I've found (and I've tested this over and over) that try/except does not perform all that well, for whatever reason. I frequently try several ways of doing things, and I don't think I've ever found a method that uses try/except to perform the best of those tested, in fact it seems to me those methods have usually come out close to the worst, if not the worst. Not in every case, but in many cases. I know a lot of people say it's the "Pythonic" way, but that's one area where I part ways with them. To me, it's neither very performant nor very elegant, so, I tend to only use it for error trapping and reporting.

我本来想抱怨PHP, perl, ruby, C，甚至是该死的shell都有简单的函数来测试字符串是否为整数，但在验证这些假设时，我被绊倒了!显然，这种缺乏是一种常见的疾病。

以下是布鲁诺的帖子的快速编辑:

import sys, time, re

g_intRegex = re.compile(r"^([+-]?[1-9]\d*|0)$")

testvals = [
    # integers
    0, 1, -1, 1.0, -1.0,
    '0', '0.','0.0', '1', '-1', '+1', '1.0', '-1.0', '+1.0', '06',
    # non-integers
    'abc 123',
    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'},
    # with spaces
    ' 0 ', ' 0.', ' .0','.01 '
]

def isInt_try(v):
    try:     i = int(v)
    except:  return False
    return True

def isInt_str(v):
    v = str(v).strip()
    return v=='0' or (v if v.find('..') > -1 else v.lstrip('-+').rstrip('0').rstrip('.')).isdigit()

def isInt_re(v):
    import re
    if not hasattr(isInt_re, 'intRegex'):
        isInt_re.intRegex = re.compile(r"^([+-]?[1-9]\d*|0)$")
    return isInt_re.intRegex.match(str(v).strip()) is not None

def isInt_re2(v):
    return g_intRegex.match(str(v).strip()) is not None

def check_int(s):
    s = str(s)
    if s[0] in ('-', '+'):
        return s[1:].isdigit()
    return s.isdigit()    


def timeFunc(func, times):
    t1 = time.time()
    for n in range(times):
        for v in testvals: 
            r = func(v)
    t2 = time.time()
    return t2 - t1

def testFuncs(funcs):
    for func in funcs:
        sys.stdout.write( "\t%s\t|" % func.__name__)
    print()
    for v in testvals:
        if type(v) == type(''):
            sys.stdout.write("'%s'" % v)
        else:
            sys.stdout.write("%s" % str(v))
        for func in funcs:
            sys.stdout.write( "\t\t%s\t|" % func(v))
        sys.stdout.write("\r\n") 

if __name__ == '__main__':
    print()
    print("tests..")
    testFuncs((isInt_try, isInt_str, isInt_re, isInt_re2, check_int))
    print()

    print("timings..")
    print("isInt_try:   %6.4f" % timeFunc(isInt_try, 10000))
    print("isInt_str:   %6.4f" % timeFunc(isInt_str, 10000)) 
    print("isInt_re:    %6.4f" % timeFunc(isInt_re, 10000))
    print("isInt_re2:   %6.4f" % timeFunc(isInt_re2, 10000))
    print("check_int:   %6.4f" % timeFunc(check_int, 10000))

以下是性能比较结果:

timings..
isInt_try:   0.6426
isInt_str:   0.7382
isInt_re:    1.1156
isInt_re2:   0.5344
check_int:   0.3452

C语言的方法可以对它进行一次扫描。我认为，用C语言来扫描字符串是正确的做法。

编辑:

我更新了上面的代码，使其能够在Python 3.5中工作，并包含了来自当前投票最多的答案的check_int函数，并使用了我能找到的当前最流行的正则表达式来测试整型。这个正则表达式拒绝'abc 123'这样的字符串。我添加了'abc 123'作为测试值。

我很有趣地注意到，在这一点上，测试的所有函数，包括try方法、流行的check_int函数和最流行的正则表达式，都没有返回所有测试值的正确答案(好吧，这取决于你认为的正确答案是什么;请参阅下面的测试结果)。

内置的int()函数无声地截断浮点数的小数部分并返回小数之前的整数部分，除非浮点数首先转换为字符串。

check_int()函数对于0.0和1.0(技术上是整数)这样的值返回false，对于'06'这样的值返回true。

以下是当前(Python 3.5)的测试结果:

              isInt_try |       isInt_str       |       isInt_re        |       isInt_re2       |   check_int   |
0               True    |               True    |               True    |               True    |       True    |
1               True    |               True    |               True    |               True    |       True    |
-1              True    |               True    |               True    |               True    |       True    |
1.0             True    |               True    |               False   |               False   |       False   |
-1.0            True    |               True    |               False   |               False   |       False   |
'0'             True    |               True    |               True    |               True    |       True    |
'0.'            False   |               True    |               False   |               False   |       False   |
'0.0'           False   |               True    |               False   |               False   |       False   |
'1'             True    |               True    |               True    |               True    |       True    |
'-1'            True    |               True    |               True    |               True    |       True    |
'+1'            True    |               True    |               True    |               True    |       True    |
'1.0'           False   |               True    |               False   |               False   |       False   |
'-1.0'          False   |               True    |               False   |               False   |       False   |
'+1.0'          False   |               True    |               False   |               False   |       False   |
'06'            True    |               True    |               False   |               False   |       True    |
'abc 123'       False   |               False   |               False   |               False   |       False   |
1.1             True    |               False   |               False   |               False   |       False   |
-1.1            True    |               False   |               False   |               False   |       False   |
'1.1'           False   |               False   |               False   |               False   |       False   |
'-1.1'          False   |               False   |               False   |               False   |       False   |
'+1.1'          False   |               False   |               False   |               False   |       False   |
'1.1.1'         False   |               False   |               False   |               False   |       False   |
'1.1.0'         False   |               False   |               False   |               False   |       False   |
'1.0.1'         False   |               False   |               False   |               False   |       False   |
'1.0.0'         False   |               False   |               False   |               False   |       False   |
'1.0.'          False   |               False   |               False   |               False   |       False   |
'1..0'          False   |               False   |               False   |               False   |       False   |
'1..'           False   |               False   |               False   |               False   |       False   |
'0.0.'          False   |               False   |               False   |               False   |       False   |
'0..0'          False   |               False   |               False   |               False   |       False   |
'0..'           False   |               False   |               False   |               False   |       False   |
'one'           False   |               False   |               False   |               False   |       False   |
<obj..>         False   |               False   |               False   |               False   |       False   |
(1, 2, 3)       False   |               False   |               False   |               False   |       False   |
[1, 2, 3]       False   |               False   |               False   |               False   |       False   |
{'one': 'two'}  False   |               False   |               False   |               False   |       False   |
' 0 '           True    |               True    |               True    |               True    |       False   |
' 0.'           False   |               True    |               False   |               False   |       False   |
' .0'           False   |               False   |               False   |               False   |       False   |
'.01 '          False   |               False   |               False   |               False   |       False   |

刚才我试着添加这个函数:

def isInt_float(s):
    try:
        return float(str(s)).is_integer()
    except:
        return False

它的性能几乎与check_int(0.3486)一样好，对于1.0和0.0以及+1.0和0这样的值，它返回true。0等等。但它也为'06'返回true，所以。我想，选择你的毒药吧。