File I/O

Reading and writing files.

Working with paths

import os

current_file = os.path.realpath('file_io.ipynb')  
print('current file: {}'.format(current_file))
# Note: in .py files you can get the path of current file by __file__

current_dir = os.path.dirname(current_file)  
print('current directory: {}'.format(current_dir))
# Note: in .py files you can get the dir of current file by os.path.dirname(__file__)

data_dir = os.path.join(current_dir, 'data')
print('data directory: {}'.format(data_dir))

current file: /Users/jerry/github/jerry-git/learn-python3/notebooks/beginner/file_io.ipynb
current directory: /Users/jerry/github/jerry-git/learn-python3/notebooks/beginner
data directory: /Users/jerry/github/jerry-git/learn-python3/notebooks/beginner/data

Checking if path exists

print('exists: {}'.format(os.path.exists(data_dir)))
print('is file: {}'.format(os.path.isfile(data_dir)))
print('is directory: {}'.format(os.path.isdir(data_dir)))

exists: True
is file: False
is directory: True

Reading files

file_path = os.path.join(data_dir, 'simple_file.txt')

with open(file_path, 'r') as simple_file:
    for line in simple_file:
        print(line.strip())

First line
Second line
Third
And so the story goes!

Writing files

new_file_path = os.path.join(data_dir, 'new_file.txt')

with open(new_file_path, 'w') as my_file:
    my_file.write('This is my first file that I wrote with Python.')

Now go and check that there is a new_file.txt in the data directory. After that you can delete the file by:

if os.path.exists(new_file_path):  # make sure it's there
    os.remove(new_file_path)