Python: raw_input and unsupported operand type(s)

问题

I am a newbie to Python and have been recently attempting to create a BMI calculator, but I am having errors with the following code:

def calculator():

    weight = raw_input('Please enter your weight (kg):')

    if weight.isdigit and weight > 0:
        height = raw_input('Please enter your height (m):') 

        if height.isdigit and height > 0:
            bmi = (weight) / (height ** 2) 

            print "Your BMI is", bmi

            if bmi < 18.5:
                print 'You are underweight.'
            if bmi >= 18.5 and bmi < 25:
                print 'Your BMI is normal.'
            if bmi >= 25 and bmi < 30:
                print 'You are overweight.'
            if bmi >= 30:
                print 'You are obese.'      

        else:   
            height = raw_input('Please state a valid number (m):')


    else:
        weight = raw_input('Please state a valid number (kg):')

Whenever I try to execute the code, I am able to enter weight and height, but I am then confronted with this error message:

Traceback (most recent call last):
  File "*location*", line 40, in <module>
    calculator()
  File "*location*", line 15, in calculator
    bmi = (weight) / (height ** 2)
TypeError: unsupported operand type(s) for ** or pow(): 'str' and 'int'

I apologize for this dumb question and error-ridden code, but I am very new to programming and appreciate any kind of help. :)

回答1:

raw_input always returns a str object. You need to explicitly convert the input to an int. You can either do

val = int(raw_input(...))

val = raw_input(...)
val = int(val)

As others have mentioned, there are many errors in your code. Here is one:

if height == exit:

Same problem with weight condition. I am just going to point out as you didn't ask about this in question so I will let you find out what the problem is :).

回答2:

Please use it this way

def calculator():

    weight = int(raw_input('Please enter your weight (kg):'))

    if weight >0 and weight > 0:
        height = int(raw_input('Please enter your height (m):')) 

        if height >0 and height > 0:
            bmi = (weight) / (height ** 2) 

            print "Your BMI is", bmi

            if bmi < 18.5:
                print 'You are underweight.'
            if bmi >= 18.5 and bmi < 25:
                print 'Your BMI is normal.'
            if bmi >= 25 and bmi < 30:
                print 'You are overweight.'
            if bmi >= 30:
                print 'You are obese.'      

        else:   
            height = int(raw_input('Please state a valid number (m):'))
        if height == exit:
            exit()

    else:
        weight = int(raw_input('Please state a valid number (kg):'))

    if weight == exit:
        exit()

You need to cast input entries to int because they are strings.

And you no longer have to check if it is a digit,

Still, I suggest you add another condition like:

if weight and height:
    #Do stuff

In case no entry was provided.

EDIT:

/!\ In case you need decimals cast them to float

回答3:

the numbers entered should be converted to float. just change the bmi = float(weight)/(float(height)** 2) You are good to go

来源：https://stackoverflow.com/questions/32276116/python-raw-input-and-unsupported-operand-types

标签

python

operands

exponent