List comprehension with append in one line

Question

I am trying to use list comprehension for a Numpy array and then append another element after. Then I noticed something strange.

a = [i for i in machine]
a.append("All")
print(a)

This returns [251, 360, 661, 662, 852, 'All']

While

a = [i for i in machine].append("All")

Returns None

Why does this returns a None object? Is there a way to do this in one line?

score 5 · Accepted Answer · answered Nov 26 '19 at 01:52

append changes the list you call it on. It doesn’t produce a new list, so it returns None to avoid confusion.

Python 3.6+, using a splat (expands an iterable) in a list literal:

a = [*machine, "All"]

previously, list concatenation with the + operator:

a = list(machine) + ["All"]

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