What Is the Difference Between [[], []] and [[]] * 2
T0 = [[]] * 2 T1 = [[], []] T0[0]. Append('Hello') Print T0 T1[0]. Append('Hello') Print T1 the Result Is [['Hello'], ['Hello']] [['Hello'], []] but I Can't...
![What Is the Difference Between [[], []] and [[]] * 2](https://www.alledaags.nl/uploads/what-is-the-difference-between-and-2_1200.jpg)
t0 = [[]] * 2
t1 = [[], []]
t0[0].append('hello')
print t0
t1[0].append('hello')
print t1
The result is
[['hello'], ['hello']]
[['hello'], []]
But I can't tell their difference.
2 Answers
When you do [[]] * 2, it gives you a list containing two of the same list, rather than two lists. It is like doing:
a = []
b = [a, a]
The usual way to make a list containing several different empty lists (or other mutable objects) is to do this:
t1 = [[] for _ in range(5)]
[[]] * 2
makes a shallow copy. Equivalent to:
x = []
t0 = [x, x]
However
t1 = [[], []]
Uses two separate empty list literals, they are completely different so mutating one obviously doesn't mutate the other
Marcus Vance is a cybersecurity auditor and technology writer dedicated to educating the public about online safety, data privacy regulations, enterprise security, and emerging cyber threats.
