Iteratively assigning variables in Python

Question

Never mind the placeholder variable names; how do I assign to D, E, and F in the way that I'm trying to do here?

print("Input 3 search coordinates")
D, E, F, = 0, 0, 0
    for axes in [[D, "Y"], [E, "X"], [F, "Z"]]:
        while True:
            try: 
                axes[0] = int(input("{}-Axis: ".format(axes[1])))
                break
            except:
                print("No, a natural number!")
        print(axes)
print(str(D) + str(E) + str(F))

This little bit of print debugging at the end outputs "000," rather than the inputs, like "444." What do I need in order to assign the inputs to the variables in the list being looped through (while also not repeating myself)?

Don't use dynamic variables, just use a container like a list or a dict — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Sep 5, 2019 at 23:01
The list element does not remember that its initial value came from the variable D; assigning a new value to the list element leaves D undisturbed. — John Gordon
– John Gordon, Commented Sep 5, 2019 at 23:05
@JohnGordon As a question of academic interest, what is the compiler doing with the first and second D? (Is there a way to turn a Python into the assembly of the C from the compilation, or would that be wildly unreadable?) — JohnnyApplesauce
– JohnnyApplesauce, Commented Sep 5, 2019 at 23:13
The way this code is organized, I don't think you can retrieve the input values, because you didn't assign a name to the outer list. The only name you have access to is axes, which will contain only the last sub-list when the for loop is finished. — John Gordon
– John Gordon, Commented Sep 5, 2019 at 23:14

Paul M. · Accepted Answer · 2019-09-05 23:03:50Z

1

def get_input(axis):
    while True:
        user_input = input(f"{axis}-Axis: ")
        try:
            axis_int = int(user_input)
        except ValueError:
            continue
        else:
            break
    return axis_int

print("Input 3 search coordinates")
x, y, z = [get_input(axis) for axis in "XYZ"]

answered Sep 5, 2019 at 23:03

Paul M.

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Trenton McKinney · Accepted Answer · 2019-09-05 23:31:12Z

1

Use a `dictionary` instead:

Replace the list with a dict, then call the key to update the value
Dictionaries are a better data type for situations where named variables (e.g. x, y, z) are being updated.
- More about Basic Data Types in Python

coor_dict = {'x': 0, 'y': 0, 'z': 0}

for k in coor_dict.keys():
    while True:
        try:
            coor_dict[k] = int(input(f'{k}-Axis: '))
            break
        except ValueError:
            print('No, a natural number!')

print(coor_dict)

Output of execution:

x-Axis:  4
y-Axis:  5
z-Axis:  6
{'x': 4, 'y': 5, 'z': 6}

edited Sep 5, 2019 at 23:31

answered Sep 5, 2019 at 23:16

Trenton McKinney

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Use a `dictionary` instead: