TypeError: 不支持的操作数类型 -: 'str' 和 'int'

Question

How come I'm getting this error?

My code:

def cat_n_times(s, n):
    while s != 0:
        print(n)
        s = s - 1

text = input("What would you like the computer to repeat back to you: ")
num = input("How many times: ")

cat_n_times(num, text)

Error:

TypeError: unsupported operand type(s) for -: 'str' and 'int'

Answer 1

1. The reason this is failing is because (Python 3) input returns a string. To convert it to an integer, use int(some_string) .

2. You do not typically keep track of indices manually in Python. A better way to implement such a function would be

   def cat_n_times(s, n): for i in range(n): print(s) text = input("What would you like the computer to repeat back to you: ") num = int(input("How many times: ")) # Convert to an int immediately. cat_n_times(text, num)

3. I changed your API above a bit. It seems to me that n should be the number of times and s should be the string .

Answer 2

For future reference Python is strongly typed<\/a> . Unlike other dynamic languages, it will not automagically cast objects from one type or the other (say from str<\/code> to int<\/code> ) so you must do this yourself. You'll like that in the long-run, trust me!

"

Answer 3

For future readers, use annotations to prevent such mistakes:

def cat_n_times(s: str, n: int):
    for i in range(n):
        print(s)


text = input("What would you like the computer to repeat back to you: ")
num = input("How many times: ")  # Convert to an int immediately.

cat_n_times(text, num)

Mypy gives a nice error:

annotations.py:9: error: Argument 2 to "cat_n_times" has incompatible type "str"; expected "int"
Found 1 error in 1 file (checked 1 source file)