Working with Files: Read, Write, and Edit Operations for AI Agents

File Operations Overview

Common file operations:

• Reading content


• Writing/creating files


• Editing existing files


• Managing file structure

Reading Files

Full File Read

# Python
with open('file.txt', 'r') as f:
    content = f.read()

# Shell
cat file.txt

Line by Line

with open('file.txt', 'r') as f:
    for line in f:
        process(line.strip())

Partial Read

For large files, read sections:

with open('large.txt', 'r') as f:
    f.seek(1000)  # Skip to position
    chunk = f.read(500)  # Read 500 chars

Writing Files

Create/Overwrite

with open('file.txt', 'w') as f:
    f.write("Hello, World!")

Append

with open('file.txt', 'a') as f:
    f.write("\nNew line")

JSON Files

import json

# Write
with open('data.json', 'w') as f:
    json.dump({"key": "value"}, f, indent=2)

# Read
with open('data.json', 'r') as f:
    data = json.load(f)

Editing Files

Replace Content

# Read
with open('file.txt', 'r') as f:
    content = f.read()

# Modify
content = content.replace('old', 'new')

# Write back
with open('file.txt', 'w') as f:
    f.write(content)

Surgical Edits

For precise edits, replace exact strings:

def edit_file(path, old_text, new_text):
    with open(path, 'r') as f:
        content = f.read()
    
    if old_text not in content:
        raise ValueError("Text not found")
    
    content = content.replace(old_text, new_text, 1)
    
    with open(path, 'w') as f:
        f.write(content)

File Management

Check Existence

import os

os.path.exists('file.txt')      # True/False
os.path.isfile('file.txt')      # Is regular file
os.path.isdir('directory')      # Is directory

Create Directories

os.makedirs('path/to/dir', exist_ok=True)

List Files

os.listdir('.')                 # List directory
os.walk('.')                    # Recursive walk

Delete

os.remove('file.txt')           # Delete file
os.rmdir('empty_dir')           # Delete empty dir
shutil.rmtree('dir')            # Delete dir + contents

Copy/Move

import shutil

shutil.copy('src.txt', 'dst.txt')
shutil.move('src.txt', 'dst.txt')

Path Handling

from pathlib import Path

path = Path('/home/user/file.txt')
path.name           # 'file.txt'
path.stem           # 'file'
path.suffix         # '.txt'
path.parent         # Path('/home/user')
path.exists()       # True/False

# Join paths
Path('/home') / 'user' / 'file.txt'

Best Practices

Use Context Managers

# Good - auto-closes
with open('file.txt') as f:
    content = f.read()

# Avoid
f = open('file.txt')
content = f.read()
f.close()  # Easy to forget

Handle Errors

try:
    with open('file.txt') as f:
        content = f.read()
except FileNotFoundError:
    print("File not found")
except PermissionError:
    print("Permission denied")

Use Appropriate Modes

'r'   # Read (default)
'w'   # Write (overwrites)
'a'   # Append
'r+'  # Read and write
'rb'  # Read binary
'wb'  # Write binary

Backup Before Destructive Edits

import shutil

shutil.copy('important.txt', 'important.txt.bak')
# Now safe to edit important.txt

Common Patterns

Config Files

import yaml

# Read
with open('config.yaml') as f:
    config = yaml.safe_load(f)

# Write
with open('config.yaml', 'w') as f:
    yaml.dump(config, f)

Log Files

import logging

logging.basicConfig(
    filename='app.log',
    level=logging.INFO
)
logging.info("Event occurred")

Temporary Files

import tempfile

with tempfile.NamedTemporaryFile(delete=False) as f:
    f.write(b"temporary content")
    temp_path = f.name

Conclusion

File operations are fundamental:

• Use context managers


• Handle errors gracefully


• Choose appropriate modes


• Back up important files

Master files for effective data management. For version-controlled file management, see Git for Agents.

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