python之如何将 "5cm"之类的字符串转换为整数

我有一个像 [2,3,4,"5cm", 6,"2.5km"] 这样的输入列表，我想要一个结果:

[2,3,4,5,6,2.5]

我想这样开始

for element in inputList: 

请您参考如下方法:

您可以使用正则表达式:

>>> import re 
>>> lis = [2,3,4,"5cm", 6,"2.5km"] 
>>> r = re.compile(r'\d+(.\d+)?') 
>>> [float(r.search(x).group(0)) if isinstance(x,str) else x  for x in lis] 
[2, 3, 4, 5.0, 6, 2.5] 

使用 ast.literal_eval 而不是 float 得到 5.0 作为 5:

>>> from ast import literal_eval 
>>> [literal_eval(r.search(x).group(0)) if isinstance(x,str) else x  for x in lis] 
[2, 3, 4, 5, 6, 2.5] 

开始你的方式:

import re 
from ast import literal_eval 
ans = [] 
r = re.compile(r'\d+(.\d+)?')            #regex to match an integer or decimal  
inputList = [2,3,4,"5cm", 6,"2.5km"] 
for element in inputList: 
   if isinstance(element, str):          #if element is a string then apply the regex 
       num = r.search(element).group(0)   
       ans.append(literal_eval(num)) 
   else: 
       ans.append(element)               #else append the element as it is 
print ans 
#[2, 3, 4, 5, 6, 2.5] 

另一种解决方案，考虑到您的输入始终有效:

>>> from string import digits 
>>> allowed = '-+.' + digits 
>>> allowed                        #allowed characters 
'-+.0123456789' 
>>> lis = [2,3,4,"5cm", 6,"2.5km"] 
>>> ans = [] 
for item in lis: 
    if isinstance(item, str): 
    # if item is a string 
        num = ''               # Initialize an empty string 
        for c in item:         # Iterate over the string, one character at time. 
            if c in allowed:   # If the character is present in `allowed` then 
                 num += c      # concatenate it to num 
            else: 
                break          # else break out of loop 
        ans.append(float(num)) # Append the float() output of `num` to `ans` or use  
                               # `ast.literal_eval` 
    else: 
        ans.append(item) 
...          
>>> ans 
[2, 3, 4, 5.0, 6, 2.5]