Comparing one list to another with ==

Question

I tried the following program in ipython

In [1]: a = (1,2,3,4,5,6,7)

In [2]: b = [1,2,3,4,5,6,7]

In [3]: a
Out[3]: (1, 2, 3, 4, 5, 6, 7)

In [4]: b
Out[4]: [1, 2, 3, 4, 5, 6, 7]

In [5]: a == b
Out[5]: False

In the above program what is the difference between a and b? Why is a==b returning False?

a is a tuple and b is a list. check this http://stackoverflow.com/questions/626759/whats-the-difference-between-list-and-tuples — user2963623, Aug 20 '14 at 07:36

famousgarkin · Answer 1 · 2014-08-20T07:53:16.853

Your a is a tuple, uses round brackets (), while your b is a list, uses square brackets [], so they are not of the same data type and the comparison fails, although they contain the same items:

>>> a = (1,2,3,4,5,6,7) # round brackets declare a tuple
>>> b = [1,2,3,4,5,6,7] # square brackets declare a list
>>> type(a)
<type 'tuple'>
>>> type(b)
<type 'list'>
>>> a == b
False

For the comparison you need to get them to be of the same type first, then you can compare the contents:

>>> list(a) == b
True
>>> a == tuple(b)
True
>>> c = [1,2,3]
>>> b == c
False

score 2 · Answer 2 · answered Aug 20 '14 at 07:36

2

a and b have different types. Instead, try these:

a == tuple(b)
list(a) == b

answered Aug 20 '14 at 07:36

John Zwinck

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1

I think it is better to not assume b is list or a is a tuple and do: `list(a) == list(b)` or `tuple(a) == tuple(b)` – Elisha Aug 20 '14 at 08:00
@Elisha: sure. In that case, tuple on both sides should be slightly faster. – John Zwinck Aug 20 '14 at 08:33

score 1 · Answer 3 · answered Aug 20 '14 at 07:36

1

You are not comparing two lists, but a list with a tuple.

In [1]: a = (1,2,3,4,5,6,7)

In [2]: b = [1,2,3,4,5,6,7]

In [3]: type(a)
Out[3]: tuple

In [4]: type(b)
Out[4]: list

answered Aug 20 '14 at 07:36

Bartosz Marcinkowski

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score 0 · Answer 4 · answered Aug 20 '14 at 07:38

In your program a is not list but tuple. That is why it is failing on the check. To check type you can use type function. You can use list function to typecast tuple to list for check as follows:

>>> a = (1,2,3,4,5,6,7)
>>> b = [1,2,3,4,5,6,7]
>>> 
>>> a == b
False
>>> type(a)
<type 'tuple'>
>>> type(b)
<type 'list'>
>>> 
>>> list(a) == b
True

Comparing one list to another with ==

4 Answers4