CODEWITHSUNDEEP
pythonloopspython-3.xfor-loopreturn
ZigZag
ZigZag

Reputation: 625

How do i return each value in a loop?

Instead of printing each sentence, i want to return it! But if i do return it will end the loop.

def printDeck(fileName):

    infile = open(fileName,'r') # open file
    contents = infile.readlines()   # read file
    infile.close()  # close file

    for sentence in contents:   # for each line in contents
        sentence = sentence.split() # eliminate spaces and turn into a list
        sentence[0], sentence[1] = sentence[1], sentence[0] # reverse order
        print('{0} of {1}'.format(sentence[0],sentence[1]))

This is the exercise im trying to solve:

Write a function called printDeck()which takes oneparameter, a file name. The function should read in the contents of the file and print it in the format shown below. For example: if 'Hearts 6' is read in from the file, the string should be printed as '6 of Hearts'. The function should return the contents of the file in list form.

Upvotes: 0

Views: 119

Answers (4)

mhawke
mhawke

Reputation: 87134

Write printDeck() as a generator that yields the strings. Then iterate over that generator to print.

You do not need to read the whole file into memory in one go with readlines(). If you open the file in a context manager (using with) then you do not need to worry about closing it - the context manager will ensure that that happens.

Reversal of the first 2 words of the sentence can be done with str.format() without bothering to actually swap the order after splitting.

You can write your code as a generator and more clearly like this:

def read_deck(fileName):
    with open(fileName) as f:    
        for sentence in f:
            yield '{0[1]} of {0[0]}'.format(sentence.split())

>>> for s in read_deck('deck.txt'):
...     print(s)

If you want all of the strings in one list, call list() on the generator:

>>> deck = list(read_deck('deck.txt'))

Upvotes: 0

pp_
pp_

Reputation: 3489

You can only return a value in a function once. But you can append your generated strings to mylst and then return mylst after the loop is finished.

mylst = []
for sentence in contents:   # for each line in contents
    sentence = sentence.split() # eliminate spaces and turn into a list
    sentence[0], sentence[1] = sentence[1], sentence[0] # reverse order
    mylst.append('{0} of {1}'.format(sentence[0],sentence[1]))

return mylst

Upvotes: 1

JulienD
JulienD

Reputation: 7293

Maybe you want to create a generator:

def printDeck():
    """return contents of file as string"""
    ...
    for sentence in contents:   # for each line in contents
        ...
        yield '{0} of {1}'.format(sentence[0],sentence[1])

Then use it as

deck = printDeck()
deck1 = next(deck)
deck2 = next(deck)
etc.

or 

for deck in printDeck():
    print(deck)

Upvotes: 4

Prune
Prune

Reputation: 77880

You cannot return a single sentence and stay in the loop. You can return a list of the swapped phrases like this:

mylst = []
for sentence in contents:   # for each line in contents
    sentence = sentence.split() # eliminate spaces and turn into a list
    phrase = sentence[1] + " of " + sentence[0]
    mylst.append(phrase)

return mylst

Upvotes: 0

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