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How to Format Strings with Named Placeholders in Python
Format a template string using named placeholders with the str.format() method and a dictionary.
def format_named(template, data):
"""Format a template string using named placeholders."""
return template.format(**data)
if __name__ == "__main__":
template = "Hello {name}, you are {age} years old and live in {city}."
data = {"name": "Alice", "age": 30, "city": "London"}
result = format_named(t…How to Use Template Strings for Substitution in Python
This code shows how to use Python's Template class for safe string substitution, replacing placeholders like $name with actual values.
from string import Template
def format_user_message(name, role, company):
template = Template("Hello $name! We are glad to have you as our $role at $company.")
return template.substitute(name=name, role=role, company=company)
if __name__ == "__main__":
result = format_user_message("Alice", "Python Develo…Template Method Pattern in Python: Define Base Class with Algorithm Steps
Create a template method base class using ABC that defines the skeleton of an algorithm while letting subclasses implement specific steps.
from abc import ABC, abstractmethod
class DataProcessor(ABC):
"""Template method that defines the skeleton of an algorithm."""
def process(self):
"""Template method - defines the sequence of steps."""
self.load_data()
self.clean_data()
self.transform_data()
self.s…How to Build a Data Helper for LLM Prompts in Python
A beginner-friendly helper class that flattens nested dictionaries, formats prompt templates, and safely parses JSON for AI/LLM pipelines.
import json
from typing import Any, Dict, List, Optional
class DataHelper:
"""Simple helper class for working with data in AI/LLM pipelines."""
def __init__(self, data: Optional[Dict[str, Any]] = None) -> None:
self.data = data or {}
def flatten(self, prefix: str = "") -> Dict[str, Any]…How to Build a Prompt Template with Variable Slots in Python
Create a reusable LLM prompt template with named variable slots using Python's string.Template class and fill them with render() calls.
from string import Template
class PromptTemplate:
def __init__(self, template_text):
self.template = Template(template_text)
def render(self, **kwargs):
return self.template.substitute(**kwargs)
if __name__ == "__main__":
template = PromptTemplate(
"You are a helpful assistant …How to Build a Zero-Shot Classification Prompt in Python
Creates a prompt for zero-shot text classification by pairing input text with candidate labels and a hypothesis template.
from typing import Dict, List
def build_zero_shot_prompt(
text: str,
candidate_labels: List[str],
hypothesis_template: str = "This is about {}.",
) -> Dict[str, List[str]]:
"""Build a prompt ready for zero-shot classification."""
return {
"sequences": text,
"candidate_labels": can…How to Render a Jinja-like Template from a Dict in Python
Replace {{placeholders}} in a string using values from a Python dict with a simple regex-based template renderer.
import re
def render_template(template, context):
pattern = re.compile(r"\{\{\s*(\w+)\s*\}\}")
def replace(match):
key = match.group(1)
return str(context.get(key, ""))
return pattern.sub(replace, template)
if __name__ == "__main__":
template = "Hello {{name}}, you have {{count}} new …How to build a mock RAG pipeline in Python
Build a minimal Retrieval-Augmented Generation pipeline that retrieves the best-matching document by keyword overlap and generates a template-based answer.
def simple_rag_pipeline(question, documents):
"""
A minimal mock RAG pipeline: retrieve relevant context, then generate an answer.
"""
# Step 1: Retrieve — mock retrieval by simple keyword scoring
scores = []
for doc in documents:
doc_words = set(doc.lower().split())
question_wo…Fill PDF Form Fields from a Mock Template in Python
Fills a PDF-style form template dictionary with user data, preserving template fields and formatting output as JSON.
import json
template = {
"first_name": "",
"last_name": "",
"email": "",
"phone": "",
"date_of_birth": "",
"address": "",
"city": "",
"state": "",
"zip_code": "",
"agree_to_terms": False
}
def fill_pdf_form(template: dict, data: dict) -> dict:
for key, value in data.items…Rotate API keys in Python by updating an .env template
Replace an old API key with a new one inside an .env template file, with a guard for missing keys.
import json
from pathlib import Path
def rotate_api_keys(env_template_path: Path, old_key: str, new_key: str) -> None:
"""Replace an old API key with a new one in an .env template file."""
content = env_template_path.read_text()
if old_key not in content:
print(f"Error: '{old_key}' not found in {e…How to Create a Git Commit with Message Template in Python
Run a git commit from Python using a standardized message template built from a commit type and description.
import subprocess
import sys
def commit_with_template(commit_type: str, description: str) -> None:
message = f"{commit_type}: {description}"
try:
subprocess.run(["git", "commit", "-m", message], check=True)
print(f"Committed: {message}")
except subprocess.CalledProcessError as e:
…Mock CDK Synth Output in Python for Template Testing
Simulate AWS CDK synth output with MagicMock to test or preview CloudFormation templates without running a real CDK app.
import json
from unittest.mock import MagicMock
def mock_cdk_synth() -> dict:
"""Simulate AWS CDK synth output for a simple S3 bucket."""
cdk_app = MagicMock()
cdk_app.synth.return_value.template = {
"Resources": {
"MyBucket": {
"Type": "AWS::S3::Bucket",
…Template Method Workflow Steps Base Class in Python
Define a reusable workflow skeleton in a base class and let subclasses fill in each step with the Template Method design pattern.
from abc import ABC, abstractmethod
class DataPipeline(ABC):
"""Template Method pattern: defines a workflow skeleton."""
def run(self):
"""Template method - defines the algorithm's structure."""
result = {"extracted": False, "transformed": False, "loaded": False}
raw_data = self._ext…Browse by section
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Samples are quick reference — one concept per page. For step-by-step teaching, use our Python tutorials. To test yourself, try quizzes or coding challenges. Clean up style with the Python formatter.