读取文件的下一行以确定是否打印当前行

Question

I'm trying to write this program slicer program in python, but this little bit is taking me forever to figure out.

I want to read certain file line by line and only print the lines that affect a certain variable. In this case num

this is the text file I'm reading from:

a = 3
b = 4
num = 0

while a > b:
    if a > b:
        a = a +2
        b = b + 1

        if a > 2:
            num-=1

My python file that has to read this file ^ and it has to isolate the variable num by printing the lines that contain the variable num and the loop statements where num is inside. This is the output I expect:

num = 0

while a > b:
    if a > b:
        if a > 2:
            num-=1

This is my code so far and the part of the code that is in charge of reading the lines inside the loops is not working:

# Open file
    file = open('text.py', 'r')
    Lines = file.readlines()
    count = 0
    word = "num"
    # Store all the loop statements that can appear in the file
    keyword = ["while", "for", "if", "else", "elif", "def"]

    for i in range(len(Lines)):
        count += 1

        # if line contains keyword
        if any(word in Lines[i] for word in keyword):
            # read lines inside the loop
            # count_indent is a function that counts the indent of the line to compare it and see if the line is inside the loop or not. I didn't added to the question shorter
            line_indent = count_indent(Lines[i])+4
            while i <= len(Lines) and count_indent(Lines[i + 1]) == line_indent:

                # if word appears in the next lines that are inside the loop then we print the loop statement
                if word in Lines[i + 1]:
                    print(str(count) + " : " + Lines[i])

                else:
                    break

                # move to next line inside the loop
                i = i + 1


        # If line is not empty and contains word
        if Lines[i] != '\n' and word in Lines[i]:
            print(str(count) + " : " + Lines[i])

Answer 1

This code output is similar to what you expect.

file = open('text.py', 'r', newline = '\n')
lines = file.readlines()
word = "num"
keyword = ["while", "for", "if", "else", "elif", "def"]

with open('out_text.py', 'wt') as fout:
    
    for line in lines:

        if any(word in line for word in keyword):

            fout.write(line + '\n')

        elif word in line:

            fout.write(line + '\n')