使用python脚本在txt文件中定义变量

Question

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.

i want to update the variables in the text file based on arguments passed to the python script

txt file maybe like this :

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

must var1,var2 define by the user with some input in the python script and i take result(var1-var2 for ex)

i can to do this easy but i dont know how to connect arguments from the python script to txt.

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.

Answer 1

This is a different way using regex and a dictionary, and taking input using sys.argv :

import sys,re
v1 = sys.argv[1]
v2 = sys.argv[2]

with open('file.txt','r') as f:
    content = f.read()

repl = {'var1':v1, 'var2':v2}

repl_pattern = re.compile(r'(' + '|'.join(repl.keys()) + r')')
final_data = repl_pattern.sub(lambda x: repl[x.group()], content)

with open('file.txt','w') as new:
    new.write(final_data)

results:

The file.txt initially had the following content:

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

and after running the above code (with: sys.argv[1]=2 and sys.argv[2] =3) the file changed to:

input number 1= 3
input number 2= 2
result = vresult(3-2)

If you want result = 1 instead of result = vresult(3-2) then add this code:

result = str(int(v1)-int(v2))
key3 = 'vresult('+v1+'-'+v2+')'
final_data = final_data.replace(key3,result)

just before the with open('file.txt','w') as new: ....

Answer 2

There's almost certainly a better way to do this but it sounded like an interesting problem so I decided to give it a try. I defined a text file with variable names listed as such:

newfile.txt:

x = 1
y = 2
z = 3

By reading one line at a type and conforming to the "var = value" input format, you can parse the text file for the correct variable then re-write the file with the new value.

import fnmatch


var2change = "z = 17"
identifier = var2change.split('=')[0] # Get variable name

# Read file
file = open('newfile.txt', 'r')
fileLines = file.read()
fileLines = fileLines.splitlines()

for lineNum,var in enumerate(fileLines):
    if fnmatch.fnmatch(str(var),''.join([identifier,'*'])): break # Found variable to change

file.close()

file = open("newfile.txt", "w")
for ln, data in enumerate(fileLines):
    if ln == lineNum:
        lineToWrite = ''.join([var2change, '\n'])
    else:
        lineToWrite = ''.join([data, '\n'])

    file.write(lineToWrite)

file.close()

This will re-write the file to read:

newfile.txt:

x = 1
y = 2
z = 17

Answer 3

parameter.txt file contains:

variable1=10
variable2=20

Below is the python code:

variable1=0
variable2=0
with open('parameters.txt') as f:
    para_list = [i.strip() for i in f.readlines()]
    for para in para_list:
        exec(para)
    print('sum = {}'.format(variable1+variable2))

Below is the result:

sum = 30