How to get function to create and return a list of a specified length

Question

I am having troubles getting my function to return a specified length containing repetitions of a specific value.

Example.

def myString(v, 5)
>>> v v v v v

score 2 · Answer 1 · answered Jan 21 '14 at 20:01

2

Use multiplication:

>>> v = 'v'
>>> v * 5
'vvvvv'

If you need spaces in between, use a list and join the output with a space:

>>> ' '.join([v] * 5)
'v v v v v'

answered Jan 21 '14 at 20:01

Martijn Pieters

1,048,767
296
4,058
3,343

@thg435: That feels wrong to me; build a string, then build a *new* string minus one character. – Martijn Pieters Jan 21 '14 at 20:07
`'v ' * 4 + 'v'` then ;) – georg Jan 21 '14 at 20:10
@thg435: That also constructs 2 strings for the price of one. :-P – Martijn Pieters Jan 21 '14 at 20:11
Yep, but that's 3 times faster than join! And... constructing a list just to join it is not memory-friendly either. ;-] – georg Jan 21 '14 at 20:24
@thg435: but [faster than a generator expression](http://stackoverflow.com/a/9061024/100297) when used with `str.join()`. – Martijn Pieters Jan 21 '14 at 21:29

score 0 · Answer 2 · answered Jan 21 '14 at 20:33

The syntax for your definition is wrong, which may be causing some of your trouble. Here is a complete function that will run with the join() command:

def makestring(mychar, num):
   return " ".join([mychar] * num)

makestring('v', 5)

If you are trying to learn the language, here is another example that may help. The version below is much less efficient, but builds the string in a manner that may be easier to follow. You should be able to see how the string is built one character at a time:

def makestring(mychar, num):
    mystr = ""
    for i in range(num-1):
        mystr = mystr + mychar + " "
    mystr = mystr + mychar
    return mystr

makestring('v', 5)

How to get function to create and return a list of a specified length

2 Answers2