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Day 6: File Handling

Topics

Reading and Writing Files in Python
File Modes
File Handling Exceptions

Reading Files

In Python, you can read from a file using the built-in open() function with the r mode (read mode).

# Open the file in read mode
file = open('example.txt', 'r')
content = file.read()
print(content)
file.close()

Writing to Files

To write data to a file, you use the open() function with the w (write) or a (append) mode.

# Open the file in write mode (it will overwrite existing content)
file = open('example.txt', 'w')
file.write("Hello, world!")
file.close()

# Open the file in append mode
file = open('example.txt', 'a')
file.write("\nAppended text.")
file.close()

File Modes

'r': Read (default mode)
'w': Write (creates or overwrites the file)
'a': Append (adds content to the file without overwriting)
'b': Binary mode (used for non-text files like images)
'x': Exclusive creation (creates a new file, returns an error if the file exists)

File Handling Exceptions

When working with files, it’s a good idea to handle potential errors (e.g., file not found) using try-except blocks.

try:
    file = open('nonexistent_file.txt', 'r')
    content = file.read()
    print(content)
except FileNotFoundError:
    print("The file does not exist.")
finally:
    if file:
        file.close()

Exercises for Day 6

Exercise 1: Count the Number of Words in a File

Write a program that:

Opens a text file.
Reads the file and counts the number of words in it.

def count_words_in_file(file_name):
    with open(file_name, 'r') as file:
        content = file.read()
        words = content.split()
        return len(words)

print(count_words_in_file('example.txt'))

Exercise 2: Log Errors to a File