字符串中的数字总和

问题描述

如果我只是在这里阅读我的 sum_digits 函数，这在我的脑海中是有道理的，但它似乎产生了错误的结果.有什么建议吗?

if i just read my sum_digits function here, it makes sense in my head but it seems to be producing wrong results. Any tip?

def is_a_digit(s):
''' (str) -> bool

Precondition: len(s) == 1

Return True iff s is a string containing a single digit character (between
'0' and '9' inclusive).

>>> is_a_digit('7')
True
>>> is_a_digit('b')
False
'''

return '0' <= s and s <= '9'

def sum_digits(digit):
    b = 0
    for a in digit:
        if is_a_digit(a) == True:
            b = int(a)
            b += 1

    return b

对于函数sum_digits，如果我输入sum_digits('hihello153john')，它应该产生9

For the function sum_digits, if i input sum_digits('hihello153john'), it should produce 9

推荐答案

请注意，您可以使用内置函数轻松解决此问题.这是一个更惯用和更有效的解决方案:

Notice that you can easily solve this problem using built-in functions. This is a more idiomatic and efficient solution:

def sum_digits(digit):
    return sum(int(x) for x in digit if x.isdigit())

print(sum_digits('hihello153john'))
=> 9

特别要注意，对于字符串类型已经存在 is_a_digit() 方法，它被称为 isdigit().

In particular, be aware that the is_a_digit() method already exists for string types, it's called isdigit().

sum_digits() 函数中的整个循环可以使用生成器表达式作为 sum() 内置函数的参数更简洁地表示，如如上所示.

And the whole loop in the sum_digits() function can be expressed more concisely using a generator expression as a parameter for the sum() built-in function, as shown above.

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