define variables in the txt file using python

[Xristos Xristoou]

hello


i have one .txt file and i want to create python script with sys.argv or argparse or other package to define some variables in the txt file and i take some result.



txt file maybe like this :

input number 1= %var1%
input number 2= %var2%
result = %vresult(var1-var2)%

how can i write a python script to update dynamic variables in the txt file ?
i dont want with replace i thing so arguments is the better.