Appending lines for existing file in python

Sunday, 6 January 2019

Answer

I want to add lines to an existing file in python. I wrote the following two files

print_lines.py

while True:
    curr_file = open('myfile',r)
    lines = curr_file.readlines()
    for line in lines:
        print lines

add_lines.py

curr_file = open('myfile',w)
curr_file.write('hello world')
curr_file.close()

but when I run first print_lines.py and then add_lines.py I don't get the new line I add. How can I solve it?

Answer

The issue is in the code -

curr_file = open('myfile',w)
curr_file.write('hello world')
curr_file.close()

The second argument should be a string, which indicates the mode in which the file should be openned, you should use a which indicates append .

curr_file = open('myfile','a')
curr_file.write('hello world')
curr_file.close()

w mode indicates write , it would overwrite the existing file with the new content, it does not append to the end of the file.