将float变量转换为字符串

Question

I'm trying to convert a variable whose value changes however the value is usually to one decimal place eg 0.5. I'm trying to change this variable to 0.50. I'm using this code but when I run the program it says TypeError: Can't convert 'float' object to str implicitly

Here is my code:

while topup == 2:
    credit = credit + 0.5
    credit = str(credit)
    credit = '%.2f' % credit
    print("You now have this much credit £", credit)
    vending(credit)

Answer 1

while topup == 2:
    credit = float(credit) + 0.5
    credit = '%.2f' % credit
    print("You now have this much credit £", credit)
    vending(credit)

the problem is you cannot float format a string

"%0.2f"%"3.45"  # raises error

instead it expects a number

"%0.2f"%3.45   # 0k
"%0.2f"%5   # also ok

so when you call str(credit) it breaks the format string right below (that incidentally also casts credit back to a string)

incidentally you should really only do this when you print

credit = 1234.3
print("You Have : £%0.2f"%credit)

in general you want your credit to be a numeric type so that you can do math with it