A program which will modify another program by using python 3

Question

I am trying to write a program in python which will modify another python program. Steps will be as follows:

1. I have a program (pyh.py) which contains below-mentioned lines and output is as follows

output:

Number of lines: 6 
Number of characters: 65

code for pyh.py :

import os
import sys

def pyh( filename ):

    if ( os.path.isfile( filename ) ):

        file = open( filename, 'r' )
        line_list = file.readlines()
        pyh_compute_size( line_list )
        file.close()

    else:
        print( "File " + filename + " does not exist." )


def pyh_compute_size( line_list ):

    line_count = 0; char_count = 0
    for line in line_list:

        line_count += 1
        char_count += len( line )

    print( "Number of lines: " + str( line_count ) )
    print( "Number of characters: " + str( char_count ) )


if __name__ == '__main__':

    pyh( "text_a.txt" )

2. What I am trying to do is, I am writing another python program called ' modifier.py ' which will open ' pyh.py ' (in the same directory) and read the file then close it.
3. Then open the same file ' pyh.py ' for writing. It will go through the list of line and write line 1 to 20 in the new file ( modifier.py ). After that, it removes the newline from the end of it, and add; print ("Additional Part" ) to the end, and then add a newline.
4. After that, it will write from 21 to end to the new file ( modifier.py ).

When I run the 'modifier.py' it will modify the 'pyh.py' (for line between 20 & 21). When 'pyh.py' is modified then it should show the below output.

Additional Part
Additional Part
Number of lines: 6 
Number of characters: 65

I am trying to do the step 3 & 4 but unable to find the appropriate way. I am new in python. So it would be really great if someone helps me to solve it.

code for modifier.py is as follow:

import os
import sys


def pyh_new( filename ):

    if ( os.path.isfile( filename ) ):

        file = open( filename, 'r' )
        line_list = file.readlines()
        file.close()

def pyh_new( filename ):

    if ( os.path.isfile( filename ) ):

        file = open( filename, 'w' )
        line_list = file.writelines()
        #need to write 

        file.close()



if __name__ == '__main__':

    pyh_new( "pyh.py" )

Answer 1

You have pyh_new listed twice. What you could do is call the name of the first one phy_new_read, and the second one phy_new_write. Then you would want to make phy_new_read return the line_list. return line_list . You would then be able to do:

if __name__ == '__main__':

    lines = pyh_new_read( "pyh.py" )

    #grab the specific lines that you want. See 
    # https://stackoverflow.com/questions/2081836/reading-specific-lines-only-python

    pyh_new_write( lines )

See the following question for how to get specific lines from a file Reading specific lines only (Python)