How to use a variable dynamically from an imported module in python 3.8

Question

I currently have the following file load.py which contains:

readText1 = "test1"
name1 = "test1"

readText1 = "test2"
name1 = "test2"

Please note that the number will change frequently. Sometimes there might be 2, sometimes 20 etc.

I need to do something with this data and then save it individually.

In my file I import load like so:

from do.load import *
#where do is a directory

I then create a variable to know how many items are in the file (which I know)

values = range(2)

I then attempt to loop and use each "variable by name" like so:

for x in values:
    x = x + 1
    textData = readText + x
    nameSave = name + x

Notice I try to create a textData variable with the readText but this won’t work since readText isn’t actually a variable. It errors. This was my attempt but it’s obviously not going to work. What I need to do is loop over each item in that file and then use it’s individual variable data. How can I accomplish that?

Asked By: FabricioG

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Source

Answer 1

The file load.py will load only the last variable "readText1" and "name1".

To do what you are asking for, you have to open load.py file as a text file and then iterate over each line to get 2 variables ("readText1" and "name1") for each iteration.

Answered By: Xrayman

Answer 2

This is a common anti-pattern that you are stepping into. Every time you think "I’ll dynamically reference a variable to solve this problem" or "Variable number of variables!" think instead "Dictionary".

load.py can instead contain a dictionary:

 load_dict = {'readText1':'test1','name1':'test1','readText2':'test2','name2':'test2'}

You can make that as big or small as you want.

Then in your other script

from do.load import *

#print out everything in the dictionary
for k,v in load_dict.items():
    print(k,v)

#create a variable and assign a value from the dictionary, dynamically even
for x in range(2):    
    text_data = load_dict['readText' + x]
    print(text_data)
    x+=1

This should allow you to solve whatever you are trying to solve and won’t cause you the pain you will find if you continue down your current path.

Answered By: JNevill

Answer 3

If you are trying to access the variables in the module you’ve imported, you can use dir.

loader.py

import load

values = dir(load) # All the values in load.py

# to get how many they are
num_vars = len([var for var in module_vars if not var.startswith("__")])
print(num_vars)

# to get their names
var_names = [var for var in module_vars if not var.startswith("__")]
print(var_names)

# to get their values
var_values = [globals()[f"module.{var}"] for var in var_names]
print(var_values)

However, it is unsafe as it may introduce security vulnerabilities to your code. It is also slower. You can use data structures as JNevil has said here, here

Answered By: mariko

How to use a variable dynamically from an imported module in python 3.8

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