Type casting many variables in python

Question

Possibly wrong terminologies here, please correct me.

Problem:
I have many objects, say lists of integers a=[1,3,7], b=[1,9], c... etc. I want to convert each to an np.array for instance.

So far:
What works: Explicitly convert individually:

a=np.array(a)
b=np.array(b)
...

What did not work:
[np.array(x) for x in [a,b,c...]] which only gives a list of the arrays (ok, that was expected) but does not change the variable a,b... to be of type np.array.

I am aware this unveils how little I know about python basics (what is pointer, what is reference etc...too long ago where I learned about it for c++).

a,b,c = [np.array(x) for x in [a,b,c...]][np.array(x) for x in [a,b,c]] (but i second chepners comment) — Joran Beasley
– Joran Beasley, Commented Dec 22, 2021 at 20:53
Obligatory reading: nedbatchelder.com/text/names.html. You probably don't want individual names in the first place, but a dict whose keys you can iterate over in order to reassign to the same keys. for k, v in d.items(): d[k] = np.array(v). — chepner
– chepner, Commented Dec 22, 2021 at 20:53
Type casting, in the sense of changing the type of an object, does not generally work in Python. In some cases you can change the .__class__ of an object, but that won't work between lists and arrays. — MisterMiyagi
– MisterMiyagi, Commented Dec 22, 2021 at 20:57

Mureinik · Accepted Answer · 2021-12-22 20:54:40Z

2

You have the right idea, but as you've seen, np.array(x) will create a new array based on x, not modify x itself. Having said that, you can assign these values back to the original variables:

a,b,c,etc=[np.array(x) for x in [a,b,c,etc]]

answered Dec 22, 2021 at 20:54

Mureinik

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