How to Build and Deploy a Web-Based Calculator using Flask in Docker Environment
- Sharon Rajendra Manmothe
- 1 day ago
- 2 min read
Create a folder named: python-calculator
python-calculator/
│
├─ app.py
├─ requirements.txt
├─ Dockerfile
├─ docker-compose.yml
└─ templates/
└─ index.html
app.py (Flask app)
from flask import Flask, render_template, request
app = Flask(__name__)
@app.route('/')
def home():
return render_template("index.html")
@app.route('/calculate', methods=['POST'])
def calculate():
try:
a = float(request.form.get('a'))
except:
a = None
try:
b = float(request.form.get('b'))
except:
b = None
op = request.form.get('op')
result = None
error = None
try:
if op == "add":
result = a + b
elif op == "sub":
result = a - b
elif op == "mul":
result = a * b
elif op == "div":
if b == 0:
raise ValueError("Division by zero")
result = a / b
elif op == "pow":
result = a ** b
elif op == "sqrt":
if a < 0:
raise ValueError("Square root of negative")
import math
result = math.sqrt(a)
elif op == "percent":
if b is not None:
result = (a / 100) * b
else:
result = a / 100
else:
error = "Invalid Operation"
except Exception as e:
error = str(e)
return render_template("index.html", a=a, b=b, result=result, error=error)
if __name__ == '__main__':
app.run(host="0.0.0.0", port=5000)index.html
<!DOCTYPE html>
<html>
<head>
<title>Python Full Calculator</title>
<style>
body { font-family: Arial; margin: 40px; }
.card { max-width: 450px; padding: 20px; border-radius: 10px; box-shadow: 0 0 8px gray; }
input { width: 100%; padding: 10px; margin: 8px 0; }
button { padding: 10px 12px; margin: 4px; }
.result { font-weight: bold; margin-top: 10px; }
.error { color: red; margin-top: 10px; }
</style>
</head>
<body>
<div class="card">
<h2>Python Calculator (Flask + Docker)</h2>
<form action="/calculate" method="POST">
<label>Number A</label>
<input type="text" name="a" placeholder="Enter number A" value="{{ a }}">
<label>Number B</label>
<input type="text" name="b" placeholder="Enter number B" value="{{ b }}">
<button type="submit" name="op" value="add">A + B</button>
<button type="submit" name="op" value="sub">A - B</button>
<button type="submit" name="op" value="mul">A × B</button>
<button type="submit" name="op" value="div">A ÷ B</button>
<button type="submit" name="op" value="pow">A ^ B</button>
<button type="submit" name="op" value="sqrt">√A</button>
<button type="submit" name="op" value="percent">A % of B</button>
</form>
{% if result %}
<div class="result">Result: {{ result }}</div>
{% endif %}
{% if error %}
<div class="error">Error: {{ error }}</div>
{% endif %}
</div>
</body>
</html>requirements.txt
Flask==3.0.0
Dockerfile
FROM python:3.10-slim
WORKDIR /app
COPY . .
RUN pip install --no-cache-dir -r requirements.txt
EXPOSE 5000
CMD ["python", "app.py"]
docker-compose.yml
version: "3.8"
services:
calculator:
build: .
container_name: python-calculator
ports:
- "5000:5000"
restart: unless-stopped
Run on Windows
Open PowerShell or CMD inside python-calculator folder:
Step 1 — Build Docker image
docker-compose up --build
Step 2 — Open in browser
Visit: http://localhost:5000
Stop container:
docker-compose down
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