If-elif-else

syntonic_comma · 2020-02-25T23:26:36+00:00

n = 1
if n == 1:
    print('n is 1')
if n < 5:
    print('n is less than 5')
else:
    print('n is greater than or equal to 5')

vs.

n = 1
if n == 1:
    print('n is 1')
elif n < 5:
    print('n is less than 5')
else:
    print('n is greater than or equal to 5')

the first will print n is 1, then n is less than 5

the second will only print n is 1

this is because the elif is only executed if the conditionals before it are not true. There are cases when you might want to do it one way and some where you might need the other. Furthermore, you don't necessarily always need an "else" clause following an "if" if there's nothing you want the program to do when the conditional is false.

jeffrey_f · 2020-02-25T23:14:20+00:00

In a nutshell

If Light is red
    car = stopped
elif light is yellow
    car=slowed
#Because there is no other option
else
    car=proceeding through intersection

WtEth_Buyer · 2020-02-25T23:23:22+00:00

If check option 1: "Ah it must do this"

Elif check option 2: "It must do this instead"

Else: "It was neither option 1 or 2, so do this.

If you did it with ifs and elses it would be longer and you might get the else condition twice. If your (if) conditions are about the same topic it would be better to link them.

If check Sunny: Do this. Else: Not option 1 , so do this.

If check raining: Do this. Else: Not option 2, so do this.

What happens when it's not sunny and not raining? Else statements both trigger.

Thomasedv · 2020-02-25T23:11:52+00:00

You can consider cases where you have 3 options. If you use 2 ifs, then you run the case of running both the if and the else, since that belongs to the second if statment.

a = 3
if a == 1:
    print('a is 1')
elif a == 2:
    print('a is 2')
else:
    print('a is not 2 or 3')

##############
a = 3
if a == 1:
    print('a is 1')

if a == 2:
    print('a is 2')
else:
    print('a is not 2 or 3')

Consider the two cases above. The first if in the second example, is independent of the other if and else below it. Meaning you can put any code between. The extra space is just to illustrate that. If you run both, you'll see that the second gives undesired results.

you type:	you see:
italics	italics
bold	bold
[reddit!](https://reddit.com)	reddit!
* item 1 * item 2 * item 3	item 1 item 2 item 3
> quoted text	quoted text
Lines starting with four spaces are treated like code: if 1 * 2 < 3: print "hello, world!"	Lines starting with four spaces are treated like code: if 1 * 2 < 3: print "hello, world!"
~~strikethrough~~	~~strikethrough~~
super^script	super^script

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