HELP

Question

x=[[],[],[]]
x[0]=1 -> this I get
x[2]=x[1].append(str(x[0])) -> this I totally don’t
print(x)

Result is:

[1,[’1’], None]

Why is it none?

First [] becomes 1
Second [] becomes ’1’??
Third [] becomes ?? none? Why?

Answer 1

x[1].append(str(x[0])) appends the string value of x[0] to x[1], and does nothing else. Meaning, it doesn't return anything. So when you set the value of x[2] to that, it becomes None.

Answer 2

append is a list method that modifies a list but returns nothing (None). in other words, its result is a modified list itself, it has nothing to return.

>>> a=[1]
>>> b=2
>>> c=a.append(b)
>>> print(a)
[1, 2]
>>> print(c)
None
>>>