CODEWITHSUNDEEP
pythoniteration
Seb
Seb

Reputation: 2016

Python: Using exception for iteration (beginner)

I just want to know why this doesn't work (I am trying to name the ducklings from a book: Jack, Kack, Lack, Mack, Nack, Ouack, Pack, Quack) Note: Quack and Ouack have a U

prefixes = 'JKLMNOPQ'
suffix = 'ack'

for letter in prefixes:
    if letter != 'O' or 'Q':      #I know this doesn't work, need to know alternative
        print letter + suffix
    else:
        print letter + 'u' + suffix

Upvotes: 3

Views: 188

Answers (3)

Abhijit
Abhijit

Reputation: 63737

Python is not COBOL or some other language which supports this syntax. As a start I would suggest you read Expressions.

Now coming back to your problem, what you expect from the statement

if letter != 'O' or 'Q':

definitely 

if letter != 'O' or letter != 'Q':

interestingly Python allows you to think laterally. For example you might also say,

letter not in ['O','Q']

or simply

letter not in 'OQ': #In Python Notation

or can be more expressive like

if all(letter != x for x in 'OQ'):

Just compare the above mentioned syntax and usage with yours

When you wrote 

if letter != 'O' or 'Q':

which in Python should be written as

if letter not in 'OQ':

or may even be

if all(letter != x for x in 'OQ'):

Upvotes: 2

tchap
tchap

Reputation: 1057

Please note that

if letter != 'O' or 'Q':

is in fact

if (letter != 'O') or 'Q':

That is probably not what you wanted.

Just a small test on top of it:

>>> True != False or True
True
>>> (True != False) or True
True
>>> True != (False or True)
False

Note: This means that the answer marked on top is not true, letter is not compared to the result of O or Q...

Upvotes: 5

Rafe Kettler
Rafe Kettler

Reputation: 76955

You likely mean this:

if letter != 'O' or letter != 'Q':

The result of your original statement,

if letter != 'O' or 'Q':

compared letter to the result of 'O' or 'Q', which is a boolean (true to be exact) (so you could see why this comparison would always be true as it was).

Upvotes: 7

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