[Solved] Confusing python – Cannot convert string to float

Question

The problem is exactly what the Traceback log says: Could not convert string to float

If you have a string with only numbers, python’s smart enough to do what you’re trying and converts the string to a float.
If you have a string with non-numerical characters, the conversion will fail and give you the error that you were having.

The way most people would approach this problem is with a try/except (see here), or using the isdigit() function (see here).

Try/Except

try:
    miles = float(input("How many miles can you walk?: "))
except:
    print("Please type in a number!")

Isdigit()

miles = input("How many miles can you walk?: ")
if not miles.isdigit():
    print("Please type a number!")

Note that the latter will still return false if there are decimal points in the string

EDIT

Okay, I won’t be able to get back to you for a while, so I’ll post the answer just in case.

while True:
    try:
        miles = float(input("How many miles can you walk?: "))
        break
    except:
        print("Please type in a number!")

#All of the ifs and stuff

The code’s really simple:

It will keep trying to convert the input to a float, looping back to the beginning if it fails.
When eventually it succeeds, it’ll break from the loop and go to the code you put lower down.

Accepted Answer