Build a Multi-API Caller

Instructions

1. Create a new directory for your lab and navigate into it:

   mkdir api-caller-lab
   cd api-caller-lab

2. Create and activate a virtual environment using uv:

   uv venv
   source .venv/bin/activate  # On Windows: .venv\Scripts\activate

3. Create the following files in your directory:
   • main.py (our main script)
   • requirements.txt
   • .gitignore
4. Add .venv and .env to your .gitignore file.

python -m venv .venv

Instructions

1. Add the following to your requirements.txt:

   aiohttp>=3.9.0
   pydantic>=2.7.1
   python-dotenv>=1.0.1
   requests>=2.31.0

2. Install the packages:

   uv pip install -r requirements.txt

   Or if using standard pip:

   pip install -r requirements.txt

Instructions

In main.py, define the Pydantic models that represent the data you expect from the APIs. This is your "schema."

# main.py
from pydantic import BaseModel, Field
from typing import List, Optional

# --- Models for REST Countries API ---
class CountryName(BaseModel):
    common: str
    official: str

class CapitalInfo(BaseModel):
    latlng: Optional[List[float]] = None

class CountryInfo(BaseModel):
    name: CountryName
    cca2: str  # The 2-letter country code
    capital: List[str]
    population: int
    capital_info: CapitalInfo = Field(alias='capitalInfo')

# --- Models for Public Holidays API ---
class Holiday(BaseModel):
    date: str
    local_name: str = Field(alias='localName')
    name: str
    country_code: str = Field(alias='countryCode')

Instructions

In main.py, write the coroutines to fetch data from each API.

# main.py (continued)
import asyncio
import aiohttp
from pydantic import ValidationError

async def fetch_country_info(session: aiohttp.ClientSession, country_name: str) -> Optional[CountryInfo]:
    """Fetches and validates country information."""
    url = f"https://restcountries.com/v3.1/name/{country_name}"
    print(f"Fetching data from {url}...")
    try:
        async with session.get(url) as response:
            response.raise_for_status()
            data = await response.json()
            # The API returns a list, we validate the first result
            if data:
                return CountryInfo.model_validate(data[0])
            return None
    except (aiohttp.ClientError, ValidationError, IndexError) as e:
        print(f"Error fetching or validating country data: {e}")
        return None

async def fetch_next_holiday(session: aiohttp.ClientSession, country_code: str) -> Optional[Holiday]:
    """Fetches and validates the next public holiday."""
    url = f"https://date.nager.at/api/v3/NextPublicHolidays/{country_code}"
    print(f"Fetching data from {url}...")
    try:
        async with session.get(url) as response:
            response.raise_for_status()
            data = await response.json()
            if data:
                return Holiday.model_validate(data[0])
            return None
    except (aiohttp.ClientError, ValidationError, IndexError) as e:
        print(f"Error fetching or validating holiday data: {e}")
        return None

Instructions

In main.py, write the main coroutine that orchestrates the API calls and displays the results.

# main.py (continued)
async def main(country_name: str):
    """Main function to orchestrate API calls and display results."""
    async with aiohttp.ClientSession() as session:
        # First, get country info to find the country code
        country_data = await fetch_country_info(session, country_name)

        if not country_data:
            print(f"\nCould not retrieve information for '{country_name}'. Exiting.")
            return

        # Now, use the country code to get the next holiday
        holiday_data = await fetch_next_holiday(session, country_data.cca2)

        # Display formatted output
        print("\n---------------------------------")
        print(f"Information for: {country_data.name.official}")
        print("---------------------------------")
        print(f"Capital: {', '.join(country_data.capital)}")
        print(f"Population: {country_data.population:,}")
        print(f"Country Code: {country_data.cca2}")

        if holiday_data:
            print("\n--- Next Public Holiday ---")
            print(f"Date: {holiday_data.date}")
            print(f"Name: {holiday_data.name} ({holiday_data.local_name})")
        else:
            print("\nCould not find holiday information.")
        print("---------------------------------")

Instructions

Create the entry point for your script at the bottom of main.py:

# main.py (continued)
if __name__ == "__main__":
    country = "Canada"  # Hardcode for testing, or use input()
    print(f"Searching for information about {country}...")
    asyncio.run(main(country))

Run Your Application

python main.py

Searching for information about Canada...
Fetching data from https://restcountries.com/v3.1/name/Canada...
Fetching data from https://date.nager.at/api/v3/NextPublicHolidays/CA...

---------------------------------
Information for: Canada
---------------------------------
Capital: Ottawa
Population: 38,005,238
Country Code: CA

--- Next Public Holiday ---
Date: 2024-12-25
Name: Christmas Day (Christmas Day)
---------------------------------