Question

Within an if: loop, why do you embed further if:'s within them versus using elif:?

Answer 1

if <condition> :
do this
elif <condition> :
do that

Answer 2

elif is exclusive :- either this or that.

Answer 3

if :
if :
if:
do this

Answer 4

all conditions have to meet for the nested statement to be executed

Answer 5

As Gameshie8 said, elif isn't embedding further ifs. Instead, it's giving a range of alternatives.

The standard if statement just does something if a condition is met:

if money in pocket:
buy coffee

if/else statements do one of two things, depending on the outcome:

if coin=="heads":
return "I win"
else:
return "You lose"

if/elif/else statements allow for multiple responses to *the same issue*

if fruit=="apple":
makeApplePie()
elif fruit=="strawberry":
makeJam()
elif fruit=="raspberry":
makePavlova()
elif fruit=="orange":
makeMarmalade()
elif fruit=="banana":
makeBananaSplit()
else:
eatFruit()

Here, it's going "if this fruit isn't an apple, see whether it's a strawberry".

Embedding ifs can be used as an alternative to using if/and statements:

if fruit=="apple":
if fruit.breed=="baking":
if fruit.ripe==True:
if fruit.owner=="You":
makeApplePie()
else:
buy(fruit)
makeApplePie()
else:
waitDays(7)
elif fruit.breed=="crabapple":
makeJam(fruit)
else:
if fruit.ripe==True:
eat(fruit)
else:
waitDays(2)

could also be:
if fruit=="apple" and fruit.breed=="baking" and fruit.ripe==True and fruit.owner=="You":
makeApplePie()

but this version makes it harder to give appropriate either/or responses to each of the conditions. Basically you'd end up having further if statements lower down anyway to handle non-baking apples, or other people's fruit.

You might also use nested if statements in more complicated functions, where ifs don't follow directly from each other:

if fruit=="apple":
some_value ==True
apple_count += 1
thing = someFunction(apple_count)
if thing > 4:
doSomething()
print "text"
setAValue(thing)
fruit.desirability = getFruitMarket(fruit, apple_count)
if fruit.desirability != "High":
ignoreFruit()
else:
buyFruit()
return something

Answer 6

Got it, thanks!

Answer 7

if / elif /else are an or relationship. If this, or elif that, or else the other thing....

If / if / if is an and relationship. If this, and if that, and if the other thing....