extend two lists and take median in one line

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I'm trying to take the median of two concatenated lists, where one of the lists is the result of the numpy repeat function.

This code works fine:

from numpy import median, repeat
g = [4, 5, 6]
g.extend([i.item() for i in repeat(0, 10)])
median(g)

For some reason the above code fails if I try to do this in one line:

g = [4, 5, 6]
median(g.extend([i.item() for i in repeat(0, 10)]))

TypeError: unsupported operand type(s) for /: 'NoneType' and 'int'

I really need to do this in one line. I tried using asarray but get the same error:

from numpy import asarray
g = [4, 5, 6]
median(asarray(g.extend([i.item() for i in repeat(0, 10)])))

Above, I use item() to convert the numpy type output of repeat back to regular python types.

numpy python
1 Answers

Because g.extend() returns None, and not the extended list, you can use the + operator between lists instead:

>>> median(g + ([i.item() for i in repeat(0, 10)]))
0.0
# or, getting rid of the unnecessary list comprehension as per @xdhmoore's comment:
>>> median(g + repeat(0, 10).tolist())

Adding two lists together with + functionally does the same as .extend(), but not in place:

>>> g + ([i.item() for i in repeat(0, 10)])
[4, 5, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]


# vs:

>>> g = [4, 5, 6]

>>> g.extend([i.item() for i in repeat(0, 10)])

>>> g
[4, 5, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
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