如何将用户输入转换为浮点数或整数？

Question

So I have

inp = print(input('what is your number?'))
n = float(inp) 
for i in range(1,n):
    print('the derivativ to the', n, 'derivative is', simplify(diff(f,x,i)))

and it says I cannot do this because my n is a n.netype val and not an int or float , but it wont let me convert to either of those

Answer 1

You're getting this error because you are assigning the return value of a print function, which is None , to inp . Try this instead:

inp = input('what is your number?')
print(inp)
n = float(inp) 
for i in range(1,n):
    print('the derivativ to the', n, 'derivative is', simplify(diff(f,x,i)))

Answer 2

Code below should work for you:

n = int(input('what is your number?'))
for i in range(1,n):
    print('the derivativ to the', n, 'derivative is', simplify(diff(f,x,i)))

input returns a string which you have to explicitly convert to int, like this:

n = int(input('what is your number?'))

Answer 3

As mentioned, you pass the number input to print and then use the result of print for your variable. But print always returns None - you've lost the input. Assign the variable and print in different steps. But don't forget to manage errors. Users are notoriously bad at following instructions.

Notice also that float can't be used in the range function whose job is to emit integers. Force the user input to be an integer from the get go to avoid errors.

while True:
    inp = input('what is your number?')
    print(inp)
    try:
        n = int(inp)
        if n <= 1:
            raise ValueError("Natural numbers greater than 1 only")
        break
    except ValueError as e:
        print(f"{e}. Try again.")

for i in range(1,n):
    print('the derivativ to the', n, 'derivative is', simplify(diff(f,x,i)))