Python File Operations: Opening, Reading, Writing, and Appending Files

File I/O in Python starts with understanding encoding (commonly UTF‑8) and the concept of files as persistent storage on disks.

Files are opened using open(name, mode, encoding='UTF-8') , where mode can be 'r' (read), 'w' (write), 'a' (append), etc. If the file does not exist, 'r' raises an error while 'w' and 'a' create a new file.

Reading methods include:

f.read(num) – reads up to num bytes or the whole file if omitted.

f.readline() – reads a single line and returns it as a string (including the newline character).

f.readlines() – returns a list of all lines, each ending with a newline.

Example:

f = open('python.txt', 'r', encoding='UTF-8')
print(f.read(10))  # reads first 10 bytes
line1 = f.readline()
print(line1, type(line1))
lines = f.readlines()
print(lines, type(lines))
f.close()

Writing uses f.write('content') (buffered until f.flush() or f.close() ). The 'w' mode overwrites existing content, while 'a' appends to the end of the file.

Example of writing and flushing:

f = open('test.txt', 'w', encoding='UTF-8')
f.write('Your name')
f.flush()
f.close()

Using a context manager automatically closes the file:

with open('python.txt', 'r', encoding='UTF-8') as f:
    for line in f:
        print(line, end='')

A practical word‑count example demonstrates reading, splitting, and aggregating data:

with open('python.txt', 'r', encoding='UTF-8') as f:
    words = []
    for line in f:
        line = line.strip()
        words.extend(line.split(' '))
    print(words)
    print(words.count('itheima'))

These snippets illustrate the essential operations for handling files in Python, suitable for beginners and anyone needing a concise reference.