How to rename variables in a loop in Python [duplicate]

Question

I want to run a program in Python which loops several times, creating a NEW array each time - i.e. no data is overwritten - with the array named with a reference to the loop number, so that I can call it in subsequent loops. For instance, I might want to create arrays x0, x1, x2, ..., xi in a loop running from 0 to i, and then call each of these in another loop running over the same variables. (Essentially the equivalent of being able to put a variable into a string as 'string %d %(x)').

Answer 1

You can access the globals() dictionary to introduce new variables. Like:

for i in range(0,5):
    globals()['x'+str(i)] = i

After this loop you get

>>> x0, x1, x2, x3, x4
(0, 1, 2, 3, 4)

Note, that according to the documentation, you should not use the locals() dictionary, as changes to this one may not affect the values used by the interpreter.

Answer 2

Using a dict:

arraysDict = {}
for i in range(0,3):
    arraysDict['x{0}'.format(i)] = [1,2,3]

print arraysDict
# {'x2': [1, 2, 3], 'x0': [1, 2, 3], 'x1': [1, 2, 3]}
print arraysDict['x1']
# [1,2,3]

Using a list:

arraysList = []
for i in range(0,3):
    arraysList.append([1,2,3])

print arraysList
# [[1, 2, 3], [1, 2, 3], [1, 2, 3]]
print arraysList[1]
# [1, 2, 3]