python if and else statements error

Question

Please help me with if and else statements in python. I like to set b according to value of a.

a=5
b=0
def fname():
    #less than 5
    if (a < 5): 
        b=100
    #greater than 5 or less than 10
    elif (a >= 5) and (a <= 10):
        b=200
    #greater than 10 or less than 20
    elif (a >10) and (a <= 20):
        b=300
print (b)
fname()

Thanks

Are you calling `fname` any where ? You don't have any `else` statements anywhere — jramirez, Oct 27 '15 at 18:59
umm... do you do realize that `a` can never be simultaneously under 6 **and** over 10, right — inspectorG4dget, Oct 27 '15 at 19:15
These are the conditions: #if less than 5 b is 100; #greater than or equal 5 and less than 10 b is 200; #greater than or equal 10 and less than 20 b is 300; — Jorge Ben, Oct 27 '15 at 19:36
`print`ing `b` before calling `fname()` is not going to show changes made by `fname`. — Ethan Furman, Oct 27 '15 at 19:36

score 3 · Accepted Answer · edited May 23 '17 at 11:44

3

The b in fname is not the same b that is in the global/outer scope.

An ugly hack to make that work is to add global b inside fname.

A better way is to pass in the value for a to fname and have fname return the new value for b and assign it:

def fname(a_number):
    #less than 5
    if a_number < 5: 
        return 100
    #greater than 5 or less than 10
    elif 5 <= a_number <= 10:
        return 200
    #greater than 10 or less than 20
    elif 10 < a_number <= 20:
        return 300        

b = fname(a)

See this question for more information about scoping and Python.

edited May 23 '17 at 11:44

Community

1
1

answered Oct 27 '15 at 19:34

Ethan Furman

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Could also make the conditions more readable using comparison chaining: `elif 5 <= a_number <= 10:` – tobias_k Oct 27 '15 at 19:38
@EthanFurman: You could also change all elif's to simple if's, because each return ends the function. – VPfB Oct 27 '15 at 19:56
@VPfB: True, but if just scanning the code the `elif`s make it clear that only one branch will be executed. – Ethan Furman Oct 27 '15 at 19:58
how do i test the value of b? – Jorge Ben Oct 27 '15 at 20:27
@EthanFurman: Just found this: http://stackoverflow.com/questions/9191388/if-else-return-or-just-if-return We have just different personal preferences. – VPfB Oct 27 '15 at 20:37
if define a=5 and print (name) the result is . – Jorge Ben Oct 27 '15 at 21:09

score 0 · Answer 2 · answered Jun 22 '20 at 15:07

a = 5
b = 0


def fname():
    # less than 5
    if (a < 5):
        b = 100
        print(b)
    # greater than 5 or less than 10
    elif (a >= 5) and (a <= 10):
        b = 200
        print(b)
    # greater than 10 or less than 20
    elif (a > 10) and (a <= 20):
        b = 300
        print(b)


fname()

if u want to learn about if and else go to - https://youtu.be/no8c4KMYBdU

python if and else statements error

2 Answers2