Find and replace variable value in a .py file using another python program

Question

Here is my challenge. I have a radioConfig.py file which contains variable values which need to be changed if and when the user changes location or scan times. This would be used with students so i'm programming a GUI, pysimplegui, to change the values of those variable.

Here is what i have so far but its not working. Its replacing the variable name, not the value.

I'm using a Rpi and python3. I studied electronics and my program skills are with C. I'm not sure if this is the best way to solve my challenge nor do i know of the python options which exist that could be useful. Any help would be amazing.

#File: GuiTest.py before code is executed
freqCenter = 21000000 
freqBandwidth = 8000000
upconvFreqHz = 125000000 
fftWindow = "BlacHarr"
notes = "Test"
rtlSampleRateHz = 2000000
#-----------------------------------------------------------------------

#Program which will be a gui asking user for input values
freqCenterGUI = 20800280


with open('GuiTest.py', 'r') as file :
    filedata = file.read()

filedata = filedata.replace('freqCenter', str(freqCenterGUI).strip('()'))

with open('GuiTest.py', 'w') as file:
    file.write(filedata)

#File: GuiTest.py after code is executed
20800280 = 21000000 
freqBandwidth = 8000000
upconvFreqHz = 125000000
notes = "Test"
rtlSampleRateHz = 2000000
#-----------------------------------------------------------------------

Answer 1

I'd say: use a config file.

Modifying a script is really not good practice !

In your cfg.ini:

[_]
freqCenter = 21000000 
freqBandwidth = 8000000
upconvFreqHz = 125000000 
fftWindow = BlacHarr
notes = Test
rtlSampleRateHz = 2000000

Then use configparser:

import configparser

cfg = configparser.ConfigParser()
with open('cfg.ini', encoding='utf-8') as f:
    cfg.read_file(f)

cfg['_']['freqCenter'] = '20800280'

with open('cfg.ini', 'w', encoding='utf-8') as f:
    cfg.write(f)

EDIT:

Or, as suggested by @juanpa.arrivillaga, using a json is also a great solution !

Matter of taste... :)

Answer 2

Quick and dirty:

File 1:

freqCenter = 21000000 
freqBandwidth = 8000000
upconvFreqHz = 125000000 
fftWindow = "BlacHarr"
notes = "Test"
rtlSampleRateHz = 2000000

File 2

#Program which will be a gui asking user for input values
freqCenterGUI = "20800280"

my_dict={}
file_data=open("GuiTest.py", "r")
in_lines=file_data.readlines()
for line in in_lines:
    var, val = line.split('=')
    if var.strip() == "freqCenter":
        val = freqCenterGUI + "\n"
        
    my_dict[var]=val

f_out=open("GuiTest.py", "w")
for key,val in my_dict.items():
    f_out.write(str(key)+"="+str(val))
f_out.close()