Python array not working

Question

This is so simple! Why isnt it working?!?!?

My python program...

def main():
    mont = []
    mont[0] = "bnkj1"
    mont[1] = "bnkj2"
    mont[2] = "bnkj3"

    print(mont[0])

main()

This is what I get when running it...

Traceback (most recent call last):
  File "/Users/hunterjamesnelson/Documents/bruceArray.py", line 9, in <module>
    main()
  File "/Users/hunterjamesnelson/Documents/bruceArray.py", line 3, in main
    mont[0] = "bnkj1",
IndexError: list assignment index out of range
>>>

Thanks!

Like the error message indicates, in Python these are lists; "array", to us, means something very different and less often used. — Karl Knechtel
– Karl Knechtel, Commented Feb 3, 2014 at 23:31

mhlester · Accepted Answer · 2014-02-03 21:56:51Z

6

Python doesn't allow you to append just by assigning to an index out of the range of the list. You need to use .append instead:

def main():
    mont = []
    mont.append("bnkj1")
    mont.append("bnkj2")
    mont.append("bnkj3")

    print(mont[0])

main()

answered Feb 3, 2014 at 21:56

mhlester

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1 Comment

Hyperboreus Over a year ago

Or in his case just mont = ['bnkj1', 'bnkj2', 'bnkj3'].

Langusten Gustel · Accepted Answer · 2014-02-03 22:03:05Z

3

The problem is that you need to specify the list size when you initialize it to use it like you do. You get an error because the list you defined has length 0. So accessing on any index will be out of range.

def main():
    mont = [None]*3
    mont[0] = "bnkj1"
    mont[1] = "bnkj2"
    mont[2] = "bnkj3"

    print(mont[0])

main()

alternativ you can use .append() to increase the size and adding an element.

edited Feb 3, 2014 at 22:03

answered Feb 3, 2014 at 21:57

Langusten Gustel

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Comments

Hugh Bothwell · Accepted Answer · 2014-02-03 22:02:03Z

1

def main():
    mont = []           # <- this is a zero-length list
    mont[0] = "bnkj1"   # <- there is no mont[0] to assign to

answered Feb 3, 2014 at 22:02

Hugh Bothwell

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Hyperboreus · Accepted Answer · 2014-02-03 22:43:59Z

0

This avoids building an empty list and then appending to it thrice.

def main():
    mont = ["bnkj1", "bnkj2", "bnkj3"]
    print(mont[0])

main()

answered Feb 3, 2014 at 22:43

Hyperboreus

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