python - Cannot convert string to int in Python

Question

What's wrong with this python snippet:

for zhszam in pontok.keys():
    s = 0
    for p in pontok[zhszam]:
        if p.isdigit():
            s += int(p)
            print s
    pontok[zhszam] = s
return pontok

where pontok is {1: ['10', ' 5', ' 3', ' 10', ' 7'], 2: ['10', ' 5', ' 3', ' 10']}. It gives the following wrong output somehow:

10
10
{1: 10, 2: 10}

While the values should be the sum of the numbers.

Thanks in advance!

Answer 1

除了第一个字符串之外，每个字符串'10'都有一个前导空格，它不是数字。因此它根本没有被处理。

尝试：

for p in pontok[zhszam]:
    p = p.strip()
    # ...

Answer 2

你不应该使用str.isdigit它，它很容易坏掉。最好将 try-except 块与int().

>>> dic = {1: ['10', ' 5', ' 3', ' 10', ' 7'], 2: ['10', ' 5', ' 3', ' 10']}
for k,v in dic.iteritems():
    s = 0
    for x in v:
        try:
            s += int(x)     #raises Error if the item is not a valid number
        except:              
            pass            #leave the item as it is if an error was thrown
    dic[k] = s 
...     
>>> dic
{1: 35, 2: 28}

Answer 3

我宁愿发表评论也不愿将此作为答案，但我还没有代表。这个问题将帮助您去除那些前导空格：Python remove all whitespace in a string