how to delete the entire line if line has specific word in python

Question

i have a.txt file like this:

the pen is yellow
pen is yellow
    hi
hello

and i want to delete the entire line that include "pen" word

like this:

    hi
hello

and i tried this

with open("myfile.txt", "r") as f:
    lines = f.readlines()
with open("myfile.txt", "w") as f:
    for line in lines:
        if "pen" in line:
            f.write(line)

---------------------------AND------------------------------ how i delete just the "pen" word in the.txt file

Answer 1

First you need to put the result on another file (myfile2) and you need to print on this file the lines thats not contain "pen".

with open("myfile.txt", "r") as f:
    lines = f.readlines()
with open("myfile2.txt", "w") as f:
    for line in lines:
        if "pen" not in line:
            f.write(line)
        else:
            f.write("\n")

Second to just substitute the word use replace(,)

with open("myfile3.txt", "w") as f:
    for line in lines:
        line = line.replace("pp","")
        f.write(line)