def num(s):
    try:
        return int(s)
    except ValueError:
        return float(s)

float(x) if '.' in x else int(x)

>>> a = "545.2222"
>>> float(a)
545.22220000000004
>>> int(float(a))
545

还有正则表达式，因为有时字符串在转换为数字之前必须准备好并规范化：

import re

def parseNumber(value, as_int=False):
    try:
        number = float(re.sub('[^.\-\d]', '', value))
        if as_int:
            return int(number + 0.5)
        else:
            return number
    except ValueError:
        return float('nan')  # or None if you wish

用法：

parseNumber('13,345')
> 13345.0

parseNumber('- 123 000')
> -123000.0

parseNumber('99999\n')
> 99999.0

顺便说一句，有些东西可以验证你有一个号码：

import numbers
def is_number(value):
    return isinstance(value, numbers.Number)
    # Will work with int, float, long, Decimal

Use:

>>> str_float = "545.2222"
>>> float(str_float)
545.2222
>>> type(_) # Check its type
<type 'float'>

>>> str_int = "31"
>>> int(str_int)
31
>>> type(_) # Check its type
<type 'int'>

我用这个函数

import ast

def parse_str(s):
   try:
      return ast.literal_eval(str(s))
   except:
      return

它会将字符串转换为其类型

value = parse_str('1')  # Returns Integer
value = parse_str('1.5')  # Returns Float