Working with Files in Python

Working with Files in Python

Python allows you to create, read, write, and manipulate files using built-in functions. Files can be text files or binary files.

Opening a file:
Use the open() function with the file name and mode.
Example:
file = open("example.txt", "r") # open file in read mode

File modes:

• "r" → read (default), file must exist

• "w" → write, creates file or overwrites if exists

• "a" → append, adds content to the end

• "x" → create, fails if file exists

• "b" → binary mode

• "t" → text mode (default)

• "+" → read and write

Reading from a file:

• read(): reads entire content

• read(size): reads specified number of characters

• readline(): reads one line

• readlines(): reads all lines into a list
  Example:
  file = open("example.txt", "r")
  content = file.read()
  print(content)
  file.close()

Writing to a file:

• write(string): writes a string to the file

• writelines(list_of_strings): writes a list of strings
  Example:
  file = open("example.txt", "w")
  file.write("Hello Python\n")
  file.writelines(["Line 1\n", "Line 2\n"])
  file.close()

Appending to a file:
Example:
file = open("example.txt", "a")
file.write("This is appended text\n")
file.close()

Closing a file:
Always close a file to free system resources.
Example:
file.close()

Using with statement:
Automatically handles closing the file.
Example:
with open("example.txt", "r") as file:
content = file.read()
print(content)

Checking if a file exists (optional):
Use the os module.
Example:
import os
if os.path.exists("example.txt"):
print("File exists")
else:
print("File does not exist")

File pointer methods:

• tell(): returns current position

• seek(position): moves pointer to specified position

Reading large files efficiently:
Use a loop to read line by line.
Example:
with open("example.txt", "r") as file:
for line in file:
print(line.strip())