Syntax error when casting string to int [duplicate]

Question

My code:

def digit_sum(n):
    result = 0
    s = str(n)
    for c in s:
        result += (int)c    # invalid syntax??????????
    return result

print digit_sum(1234)

Result:

    result += (int)c    # invalid syntax??????????
                   ^
SyntaxError: invalid syntax

The function is supposed to return the sum of each digit of the argument "n". Why do I get SyntaxError in the commented line? The variable c is of type string so it shouldn´t be an issue to apply a type cast to int.

In Python you do not cast that way.

willeM_ Van Onsem
– willeM_ Van Onsem

2017-02-25 21:27:07 +00:00
Commented Feb 25, 2017 at 21:27 — willeM_ Van Onsem
– willeM_ Van Onsem, Commented Feb 25, 2017 at 21:27

willeM_ Van Onsem · Accepted Answer · 2017-02-25 21:47:51Z

7

In Python you do not cast that way. You use:

result += int(c)

Technically speaking this is not casting: you call the int(..) builtin function which takes as input the string and produces its equivalent as int. You do not cast in Python since it is a dynamically typed language.

Note that it is of course possible that c contains text that is not an integer. Like 'the number fifteen whohaa'. Of course int(..) cannot make sense out of that. In that case it will raise a ValueError. You can use try-except to handle these:

try:
    result += int(c)
except ValueError:
    # ... (do something to handle the error)
    pass

edited Feb 25, 2017 at 21:47

answered Feb 25, 2017 at 21:27

willeM_ Van Onsem

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4 Comments

Gustavo Gomes Over a year ago

This can also throw an exception if c can't be converted into an integer. It will throw a ValueErrorexception so if possible treat it with a try-except.

willeM_ Van Onsem Over a year ago

@Gugas: that is indeed a good suggestion. I've added that tho the answer.

Gustavo Gomes Over a year ago

sorry but it's an except not a catch to pair with the try.

willeM_ Van Onsem Over a year ago

@Gugas: yeah, some brainfreeze (or being buzzy with too many things at once). Thanks.

Rok Povsic · Accepted Answer · 2017-02-25 21:27:25Z

2

In Python, you cast a string to an integer by using a function int().

    result += int(c)

answered Feb 25, 2017 at 21:27

Rok Povsic

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Comments

Umang Gupta · Accepted Answer · 2017-02-25 22:13:30Z

0

def digit_sum(n):
        numsum=[]
        add_up=str(n)
    for n in add_up[0: len(add_up)]:
        numsum.append(int(n))
    return sum(numsum)
print digit_sum(1234)

Basically, you need to cast string to integer using int(n)

edited Feb 25, 2017 at 22:13

Umang Gupta

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answered Feb 25, 2017 at 22:02

Melansia

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