Working with Files

File operations are essential for AI projects—reading prompts, saving responses, managing configurations, and processing data.

Reading Files

# Basic file reading with context manager
with open("prompt.txt", "r") as f:
    content = f.read()

# Read lines into a list
with open("data.txt", "r") as f:
    lines = f.readlines()  # Includes \n
    # Or: lines = f.read().splitlines()  # No \n

# Read line by line (memory efficient)
with open("large_file.txt", "r") as f:
    for line in f:
        process(line.strip())

Writing Files

# Write text to file
with open("output.txt", "w") as f:
    f.write("Hello, World!\n")
    f.write("Second line\n")

# Append to existing file
with open("log.txt", "a") as f:
    f.write(f"New entry: {message}\n")

# Write multiple lines
lines = ["Line 1", "Line 2", "Line 3"]
with open("output.txt", "w") as f:
    f.writelines(line + "\n" for line in lines)

Using pathlib (Modern Approach)

from pathlib import Path

# Create path object
file_path = Path("data") / "prompts" / "system.txt"

# Check if exists
if file_path.exists():
    content = file_path.read_text()

# Write to file
output_path = Path("output") / "response.txt"
output_path.parent.mkdir(parents=True, exist_ok=True)
output_path.write_text("AI response here")

# List files in directory
for file in Path("prompts").glob("*.txt"):
    print(file.name)

Common Path Operations

from pathlib import Path

path = Path("/home/user/project/data/file.json")

path.name        # "file.json"
path.stem        # "file"
path.suffix      # ".json"
path.parent      # Path("/home/user/project/data")
path.exists()    # True/False
path.is_file()   # True/False
path.is_dir()    # True/False

# Join paths
config_path = Path("config") / "settings.json"

# Get absolute path
absolute = path.resolve()

Practical AI Example

from pathlib import Path
import json

class PromptManager:
    def __init__(self, prompts_dir="prompts"):
        self.prompts_dir = Path(prompts_dir)
        self.prompts_dir.mkdir(exist_ok=True)

    def save_prompt(self, name, content):
        path = self.prompts_dir / f"{name}.txt"
        path.write_text(content)

    def load_prompt(self, name):
        path = self.prompts_dir / f"{name}.txt"
        if path.exists():
            return path.read_text()
        return None

    def list_prompts(self):
        return [p.stem for p in self.prompts_dir.glob("*.txt")]

# Usage
manager = PromptManager()
manager.save_prompt("system", "You are a helpful assistant.")
prompts = manager.list_prompts()

File Encodings

# Specify encoding (important for non-ASCII text)
with open("arabic.txt", "r", encoding="utf-8") as f:
    content = f.read()

# Or with pathlib
content = Path("arabic.txt").read_text(encoding="utf-8")

Next, we'll learn regular expressions for text processing. :::