Using Multiple If Statements with While Loop

Question

I'm trying to write a while loop that goes through a certain list looking for certain substrings. It will find words with those substrings and print out those strings.

Here is a example that works perfectly but for only one word:

lista = ['applepie','appleseed','bananacake','bananabread']

i = 0
z = len(lista)
while i < z:
    if ('pie' in lista[0+i]) == True:
        print(lista[0+i])
        break
    i = i  + 1
else:
    print('Not There Yet')

This prints out applepie (which is what is desired!).

How do I go about fixing this while loop to add in multiple constraints?

I'm trying to do this:

lista = ['applepie','appleseed','bananacake','bananabread']

i = 0
z = len(lista)
while i < z:
    if ('pie' in lista[0+i]) == True:
        print(lista[0+i])
    if ('cake' in lista[0+1]) == True:
        print(lista[0+i])
    i = i  + 1
else:
    print('Not There Yet')

This prints out: applepie Not There Yet

When I want this to print out: applepie bananacake

I used multiple 'if' statements, because I know if I want to use an 'elif', it will only run if the first 'if' statement is false.

Any help is appreciated!

'cake' in lista[0+1] should be 'cake' in lista[i] (not sure why you're adding 0... but it should be i, not 1) — Nick
– Nick, Commented Jun 3, 2020 at 3:10
Why are you doing lists like this rather than a regular for loop?!? — Mark
– Mark, Commented Jun 3, 2020 at 3:25

hrokr · Accepted Answer · 2020-06-03 03:28:20Z

1

You have two issues smallish issues and I think one larger. The first of the two small ones are what Nick and Brenden noted above. The second is your conditional. It should be <= as opposed to the < you used.

The larger seems that you're having a problem conceptualizing the actual workings. For that, let me suggest you step through it here

answered Jun 3, 2020 at 3:28

hrokr

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Comments

Mark · Accepted Answer · 2020-06-03 03:29:58Z

You can use any() to go through a list of conditions. It will evaluate to True when the condition is first met and False if it never happens. If you combine that with a regular python for loop, it will be nice a succinct:

lista = ['applepie','appleseed','bananacake','bananabread']
words = ['pie', 'cake']

for food in lista:
    if any(word in food for word in words):
        print(food)

It prints:

applepie
bananacake

You can also so the same thing as a list comprehension to get a list of words that match:

lista = ['applepie','appleseed','bananacake','bananabread']
words = ['pie', 'cake']

found = [food for food in lista if any(word in food for word in words)]
# ['applepie', 'bananacake']

Generally speaking, Python discourages you from using indices in loops unless you really need to. It tends to be error prone and harder to read.

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