Can't understand this output

Question

This is my code:

def temp(c):
    f = c * 9/5 + 32
    if c <= -273:
        print("not possible")
    else:
        return f
print(temp(-273))

It is outputting the correct answer but I can't understand why it's also printing None with it whenever the if condition is fulfilled.

When `c <= -273`, your function prints "not possible", and returns `None`. And your `print(temp(-273))` prints the return value of the function. — khelwood, Feb 26 '19 at 09:33

score 2 · Accepted Answer · edited Feb 28 '19 at 11:28

2

When we call the inbuilt print function, the function expects a value to print out. In your code when print(temp(-273)) is called, the if part of condition is executed however there is not a value returned. By default, a function which doesn't explicitly return anything returns None. That is what happens after calling the print() in your code.

edited Feb 28 '19 at 11:28

glglgl

89,107
13
149
217

answered Feb 26 '19 at 09:37

Jack

44
4

ruohola · Answer 2 · 2019-02-28T11:25:34.583

This:

def temp(c):
    f= c* 9/5 + 32
    if c <= -273:
        print(" not possible")
    else:
        return f

Is equal to this:

def temp(c):
    f= c* 9/5 + 32
    if c <= -273:
        print(" not possible")
    else:
        return f
    return None

Because functions in Python always return something, and that something is None if there is nothing else returned.

So the two cases of your if-else -block are essentially like this:

c <= -273:
    print(" not possible")
    print(None)  # the functions return value

c > -273:
    print(c * 9/5 + 32)  # the functions return value

Can't understand this output

2 Answers2