A difference of Python from R

Question

Coming from R, the following Python code does confuse me:

In [22]: a = [1, 2, 3]
In [23]: b=a
In [24]: b
Out[24]: [1, 2, 3]
In [25]: b[0]=100
In [26]: b
Out[26]: [100, 2, 3]
In [27]: a
Out[27]: [100, 2, 3]

Why does a also change although I only change b?

Possible duplicate of [python list by value not by reference](https://stackoverflow.com/questions/8744113/python-list-by-value-not-by-reference) — Jacques Kvam, Sep 23 '18 at 20:19
Possible duplicate of https://stackoverflow.com/questions/52469511/python-vs-r-scope/52469728 — G. Grothendieck, Sep 23 '18 at 20:22

score 3 · Answer 1 · answered Sep 23 '18 at 20:15

3

When you do:

b=a

You are assigning b to the same object as a, i.e. b points to the same object in memory as a

This can be verified with:

>>> b is a
True

answered Sep 23 '18 at 20:15

sacuL

1 Answers1