Python - Printing arrays using For Loop

Question

I have a multiple 2D arrays with name temp1, temp2, temp3... etc

temp1 = [[7, 2, 4],
 [5, 0, 6],
 [8, 3, 1]] 
temp2 = [[1, 1, 1],
 [1, 1, 1],
 [1, 1, 1]] 
temp3 = [[2, 2, 2],
 [2, 2, 2],
 [2, 2, 2]] 

I want to run a for loop that will return only some of the arrays depending on the range of i. I am thinking of something like

for i in range(1,3):
 arrayName = ("temp" + str(i))
 print(arrayName)

where print(arrayName) prints out the actual array instead of a string

Any help is appreciated!

Answer 1

You could do this with exec(). Also your range() should have an upper bound of your max value plus one. The upper bound is not inclusive.

for i in range(1, 4):
 exec(f'print(temp{str(i)})')

Output:

[[7, 2, 4], [5, 0, 6], [8, 3, 1]]
[[1, 1, 1], [1, 1, 1], [1, 1, 1]]
[[2, 2, 2], [2, 2, 2], [2, 2, 2]]

Answer 2

You can use eval(). It allows you to get a variable by name.

for i in range(1, 4):
 current_array = eval(f'temp{i}')
 print(current_array)

But, I advise you to set this part of code to the try/except block because you can have NameError exception. And your code will look like:

for i in range(1, 4):
 variable_name = f"temp{i}"
 try:
 current_array = eval(variable_name)
 print(current_array)
 except NameError:
 print(f"Can not get variable with {variable_name} name")

Answer 3

I notice that this is your requirement:

... where print(arrayName) prints out the actual array instead of a string

If so, you could use the following simplified design pattern:

arrays = [array1, array2, array3]
for array in arrays: 
 print(array)

And, in modification of your code, so that print() will 'print out the actual array instead of a string':

temp1 = [[7, 2, 4],
 [5, 0, 6],
 [8, 3, 1]]
temp2 = [[1, 1, 1],
 [1, 1, 1],
 [1, 1, 1]]
temp3 = [[2, 2, 2],
 [2, 2, 2],
 [2, 2, 2]]
temps = [temp1, temp2, temp3]
for i in temps:
 print(i)

Some further thoughts:

1. I would avoid the eval() or exec() Python methods as suggested by the other commenters. Simpler solutions are possible; you do not have a concrete reason to use dynamic execution.

2. There is a cleaner way to refactor your code, but I am providing the above answer that mirrors your code structure more directly so as to avoid confusion.