Python: Return list result problem in a function

Question

If I do this with print function

def numberList(items):
     number = 1
     for item in items:
         print(number, item)
         number = number + 1

numberList(['red', 'orange', 'yellow', 'green'])

I get this

1 red
2 orange
3 yellow
4 green

if I then change the print function to return function I get just only this:

(1, 'red')

why is this so?

I need the return function to work exactly like the print function, what do I need to change on the code or rewrite...thanks...Pls do make your response as simple, understandable and straight forward as possible..cheers

agf · Accepted Answer · 2011-09-16 02:30:32Z

8

return ends the function, while yield creates a generator that spits out one value at a time:

def numberList(items):
     number = 1
     for item in items:
         yield str((number, item))
         number = number + 1

item_lines = '\n'.join(numberList(['red', 'orange', 'yellow', 'green']))

alternatively, return a list:

def numberList(items):
     indexeditems = []
     number = 1
     for item in items:
         indexeditems.append(str((number, item)))
         number = number + 1
     return indexeditems

item_lines = '\n'.join(numberList(['red', 'orange', 'yellow', 'green']))

or just use enumerate:

item_lines = '\n'.join(str(x) for x in enumerate(['red', 'orange', 'yellow', 'green'], 1)))

In any case '\n'.join(str(x) for x in iterable) takes something like a list and turns each item into a string, like print does, and then joins each string together with a newline, like multiple print statements do.

answered Sep 16, 2011 at 2:30

agf

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1 Comment

djhoese Over a year ago

+1 for mentioning enumerate and your appending to a list solution (that's how I was going to answer it).

mal-wan · Accepted Answer · 2011-09-16 02:33:06Z

1

A return function will return the value the first time it's hit, then the function exits. It will never operate like the print function in your loop.

Reference doc: http://docs.python.org/reference/simple_stmts.html#grammar-token-return_stmt

What are you trying to accomplish?

You could always return a dict that had the following:

{'1':'red','2':'orange','3':'yellow','4':'green'}

So that all elements are held in the 1 return value.

edited Sep 16, 2011 at 2:33

answered Sep 16, 2011 at 2:27

mal-wan

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2 Comments

Kolly Boy Over a year ago

I understand that, what I want is stated in my question

mal-wan Over a year ago

What you want is impossible unless you capture all elements in the 1 return object as I suggested or use yield as agf suggested. A return statement ends a function - it can't return multiple times.

anujkk · Accepted Answer · 2011-09-16 02:30:37Z

0

The moment the function encounters "return" statement it stops processing further code and exits the function. That is why it is returning only the first value. You can't return more than once from a function.

answered Sep 16, 2011 at 2:30

anujkk

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1 Comment

agf Over a year ago

This doesn't help him with how to do it.

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