How to copy files in python

Copying files in Python can be efficiently handled using the shutil module, which provides a range of high-level file operations. The shutil.copy() and shutil.copy2() functions are particularly useful for this purpose. The shutil.copy() function copies the content of the source file to the destination file or directory, while shutil.copy2() does the same but also attempts to preserve file metadata such as timestamps. These functions make it straightforward to copy files with minimal code, simplifying file management tasks in Python applications.

Basic File Copying with `shutil.copy()`

Using shutil.copy():
The shutil.copy() function is one of the simplest methods for copying files in Python. It copies the content of a source file to a destination file or directory. If the destination is a directory, the file is copied into that directory with the same name. This function is sufficient for many basic file copying needs.

import shutil

source = 'path/to/source/file.txt'
destination = 'path/to/destination/file.txt'
shutil.copy(source, destination)

Error Handling:
While copying files, it is essential to handle potential errors such as the source file not existing or insufficient permissions. This can be done using try-except blocks to catch and manage exceptions.

try:
    shutil.copy(source, destination)
    print("File copied successfully.")
except FileNotFoundError:
    print("Source file not found.")
except PermissionError:
    print("Permission denied.")
except Exception as e:
    print(f"An error occurred: {e}")

Preserving Metadata with `shutil.copy2()`

Using shutil.copy2():
For situations where preserving the original file’s metadata (such as modification and access times) is important, shutil.copy2() is the preferred method. It works similarly to shutil.copy() but includes the copying of metadata.

shutil.copy2(source, destination)

When to Use shutil.copy2():
Preserving metadata can be crucial in applications where file integrity and attributes are important, such as in backup systems or when managing document archives.

Copying Directory Trees with `shutil.copytree()`

Using shutil.copytree():
To copy an entire directory tree, including all its files and subdirectories, shutil.copytree() can be used. This function recursively copies a source directory to a destination directory.

source_dir = 'path/to/source/directory'
destination_dir = 'path/to/destination/directory'
shutil.copytree(source_dir, destination_dir)

Customizing copytree():
The shutil.copytree() function allows for customization through various optional arguments, such as specifying a custom copy function or ignoring certain files and directories.

def ignore_files(directory, files):
    return ['file_to_ignore.txt']

shutil.copytree(source_dir, destination_dir, ignore=ignore_files)

Handling Large Files

Using Buffered Copy:
For large files, it might be beneficial to copy files in chunks to avoid excessive memory usage. This can be done by manually reading and writing file chunks.

def copy_large_file(source, destination, buffer_size=1024*1024):
    with open(source, 'rb') as src, open(destination, 'wb') as dst:
        while True:
            buffer = src.read(buffer_size)
            if not buffer:
                break
            dst.write(buffer)

source = 'path/to/large/source/file.txt'
destination = 'path/to/large/destination/file.txt'
copy_large_file(source, destination)

Using OS-specific Methods

Platform-specific Copying:
For certain platforms, using OS-specific commands can be more efficient. This can be done using the os module to call system-specific file copy commands.

import os

if os.name == 'posix':
    os.system(f'cp {source} {destination}')
elif os.name == 'nt':
    os.system(f'copy {source} {destination}')

Considerations:
While using OS-specific methods can be faster, they also reduce the portability of the code, making it less ideal for cross-platform applications.

Advanced File Copying

Copying with Progress Reporting:
In some applications, providing feedback on the copy progress can enhance the user experience. This can be implemented using a custom copy function that reports progress.

import os

def copy_with_progress(source, destination, buffer_size=1024*1024):
    total_size = os.path.getsize(source)
    copied_size = 0

    with open(source, 'rb') as src, open(destination, 'wb') as dst:
        while True:
            buffer = src.read(buffer_size)
            if not buffer:
                break
            dst.write(buffer)
            copied_size += len(buffer)
            print(f'Copied {copied_size / total_size:.2%} of the file.')

source = 'path/to/source/file.txt'
destination = 'path/to/destination/file.txt'
copy_with_progress(source, destination)

Ensuring Data Integrity

Verifying File Integrity:
After copying a file, verifying its integrity ensures that the copy is accurate. This can be done by comparing checksums of the source and destination files.

import hashlib

def calculate_checksum(file_path, algorithm='md5'):
    hasher = hashlib.new(algorithm)
    with open(file_path, 'rb') as file:
        while chunk := file.read(8192):
            hasher.update(chunk)
    return hasher.hexdigest()

source_checksum = calculate_checksum(source)
destination_checksum = calculate_checksum(destination)

if source_checksum == destination_checksum:
    print("File copied successfully and verified.")
else:
    print("File copy verification failed.")

Choosing the Right Hash Algorithm:
Different hash algorithms can be used depending on the security and speed requirements. MD5, SHA-1, and SHA-256 are common choices.

Using External Libraries

Exploring pathlib:
The pathlib module, introduced in Python 3.4, offers an object-oriented approach to file system paths and can be used in conjunction with shutil for file operations.

from pathlib import Path

source = Path('path/to/source/file.txt')
destination = Path('path/to/destination/file.txt')
shutil.copy(source, destination)

Benefits of pathlib:
Using pathlib can simplify path manipulations and enhance code readability, making file operations more intuitive and less error-prone.

Summary

Comprehensive File Copying:
Python provides versatile tools for copying files, from basic functions like shutil.copy() to advanced techniques involving custom buffering and integrity checks. Understanding and utilizing these methods can help in effectively managing file operations in various applications, ensuring both efficiency and security.

Basic File Copying with shutil.copy()

Preserving Metadata with shutil.copy2()

Copying Directory Trees with shutil.copytree()