CODEWITHSUNDEEP
pythonlistpython-2.7
Richie
Richie

Reputation: 49

python: when making a list of lists do i have to contain them in square brackets?

so whats the difference between: 

x = [1,1,1], [1,1,1], [1,1,1], [1,1,1]

and 

x = [[1,1,1], [1,1,1], [1,1,1], [1,1,1]]

do the square brackets around the second option do anything?

Upvotes: 1

Views: 124

Answers (4)

The6thSense
The6thSense

Reputation: 8335

x = [1,1,1], [1,1,1], [1,1,1], [1,1,1]

Will create a tuple with lists

x = [[1,1,1], [1,1,1], [1,1,1], [1,1,1]]

Will create lists of list

i.e.)

x = [1,1,1], [1,1,1], [1,1,1], [1,1,1]
x
([1, 1, 1], [1, 1, 1], [1, 1, 1], [1, 1, 1])
type(x)
<type 'tuple'>

"a","b"
('a', 'b')

Upvotes: 7

Gilbert Allen
Gilbert Allen

Reputation: 343

The first one is the same as doing this :

x = ([1,1,1], [1,1,1], [1,1,1], [1,1,1])

This is a tuple of lists.

Upvotes: 2

Tim
Tim

Reputation: 2592

Without the brackets it is a tuple:

>>> x = [1,1,1], [1,1,1], [1,1,1], [1,1,1]
>>> x
([1, 1, 1], [1, 1, 1], [1, 1, 1], [1, 1, 1])
>>> type(x)
<type 'tuple'>

You can't modify the items in a tuple.

With [] is it a list:

>>> x = [[1,1,1], [1,1,1], [1,1,1], [1,1,1]]
>>> x
[[1, 1, 1], [1, 1, 1], [1, 1, 1], [1, 1, 1]]
>>> type(x)
<type 'list'>

Upvotes: 2

Anand S Kumar
Anand S Kumar

Reputation: 90889

The first one creates a tuple of lists , while the second one creates a list of lists.

tuples are immutable, whereas lists are mutable.

Example for 1st one -

>>> x = [1,1,1], [1,1,1], [1,1,1], [1,1,1]
>>> x
([1, 1, 1], [1, 1, 1], [1, 1, 1], [1, 1, 1])
>>> x[0] = 1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment

Example for 2nd one -

>>> x = [[1,1,1], [1,1,1], [1,1,1], [1,1,1]]
>>> x
[[1, 1, 1], [1, 1, 1], [1, 1, 1], [1, 1, 1]]
>>> x[0] = 1
>>> x
[1, [1, 1, 1], [1, 1, 1], [1, 1, 1]]

Upvotes: 2

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