How to call Claude API from a python script

from pathlib import Path
from anthropic import Anthropic

# For local testing only.
API_KEY = "REDACTED"
PROMPT_FILE = "input.txt"
OUTPUT_FILE = "output.txt"

def math_problem():
    client = Anthropic(api_key=API_KEY)

    prompt = Path(PROMPT_FILE).read_text(encoding="utf-8")

    response = client.messages.create(
        model="claude-sonnet-5",
        max_tokens=500,
        system=(
            "You are a helpful math tutor. "
            "Respond in plain text only. "
            "Do not use Markdown, headings, bullet points, or LaTeX."
        ),
        messages=[
            {
                "role": "user",
                "content": prompt
            }
        ]
    )

    output_text = next(
    (block.text for block in response.content if block.type == "text"),"")

    with open("input.txt", "w") as f:
        f.write(prompt)

    with open("output.txt", "w") as f:
        for block in response.content:
            if block.type == "text":
                f.write(block.text)

    print("Prompt:")
    print(prompt)
    print("\nClaude's output:")
    print(output_text)
    print(f"\nOutput saved to {OUTPUT_FILE}")

if __name__ == "__main__":
    math_problem()

Let the brother's current age be x.
Then Sara's current age is x + 5, since she is 5 years older.

In 3 years:
Brother's age will be x + 3
Sara's age will be (x + 5) + 3 = x + 8

The sum of their ages in 3 years is 33, so:
(x + 3) + (x + 8) = 33

Combine like terms:
2x + 11 = 33

Subtract 11 from both sides:
2x = 22

Divide both sides by 2:
x = 11

So the brother is currently 11 years old.

Sara's age is x + 5 = 11 + 5 = 16

Check:
In 3 years, brother will be 14 and Sara will be 19.
14 + 19 = 33, which matches the problem statement.

Answer: Sara is currently 16 years old, and her brother is currently 11 years old.