CODEWITHSUNDEEP
pythonpython-2.7
JoesLost
JoesLost

Reputation: 41

Function to check a variable and change it

I am making a calculator to turn RGB values into Hexidecimal numbers. as I was coding I realised I had written the same code three times to check user input for red, green, and blue. So I thought, why not use a function to check my variables for me!! Here is my code:

invalid_msg = 'Whoops looks like you have entered incorrect information'
def check_rgb(var):
    while var > 255 or var < 0:
        print invalid_msg
        var = int(raw_input('Please enter a value between 0 and 255:'))
    return var

def rgb_hex():
    red = int(raw_input('Enter your value for red.'))
    check_rgb(red)
    green = int(raw_input('Enter your value for green.'))
    while green > 255 or red < 0:
        print invalid_msg
        green = int(raw_input('Enter your value for green.'))
    blue = int(raw_input('Enter your value for blue.'))
    while blue > 255 or red < 0:
        print invalid_msg
        blue = int(raw_input('Enter your value for blue.'))
    val = (red << 16) + (green << 8) + blue
    print '%s' % (hex(val)[2:]).upper()

rgb_hex()

The issue is with redeclaring the variable. Right now this stores the value entered into the function to the variable 'var' not red.

Upvotes: 1

Views: 93

Answers (3)

PM 2Ring
PM 2Ring

Reputation: 55499

As Davis Yoshida mentions, merely doing check_rgb(red) doesn't change the original value of red, since you forgot to save the value that check_rgb returns.

I recommend expanding your helper function so that it gets the user input and validates it too. Here's an example that also makes sure that the input is a valid integer in the proper range. This code also shows an easier way to print the hex representation of the RGB value. 

def get_color_byte(name):
    while True:
        s = raw_input('Enter a value from 0 to 255 for %s: ' % name)
        try:
            v = int(s)
            if not 0 <= v <= 255:
                raise ValueError('Out of range')
            return v
        except ValueError as e:
            print e

r, g, b = [get_color_byte(name) for name in ('red', 'green', 'blue')]
rgb = (r << 16) | (g << 8 ) | b
print '%06X' % rgb

test

Enter a value from 0 to 255 for red: hello
invalid literal for int() with base 10: 'hello'
Enter a value from 0 to 255 for red: 12.5
invalid literal for int() with base 10: '12.5'
Enter a value from 0 to 255 for red: -5
Out of range
Enter a value from 0 to 255 for red: 300
Out of range
Enter a value from 0 to 255 for red: 240
Enter a value from 0 to 255 for green: 13
Enter a value from 0 to 255 for blue: 7
F00D07

As an alternative to print '%06X' % rgb you could use the more modern format function:

print format(rgb, '06X')

In both of those, the capital X says to use capital letters in the hex string.

Upvotes: 0

Jalo
Jalo

Reputation: 1129

You can check the condition on the three colors calling separately the function and then compare all them in the same statement:

red_ok = check_rgb(red)
green_ok = check_rgb(green)
blue_ok = check_rgb(blue)
if (red_ok and green_ok and blue_ok) :
    val = (red << 16) + (green << 8) + blue
    print '%s' % (hex(val)[2:]).upper()

Upvotes: 0

Davis Yoshida
Davis Yoshida

Reputation: 1787

You need to do something like something like

red = check_rgb(red)

When you just do

check_rgb(red)

The return value is not used.

Upvotes: 2

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