Program 7-16: Create a user defined module basic_math that contains the following user defined functions:
1. To add two numbers and return their sum.
2. To subtract two numbers and return their difference.
3. To multiply two numbers and return their product.
4. To divide two numb

Question

Program 7-16: Create a user defined module basic_math that contains the following user defined functions:
1. To add two numbers and return their sum.
2. To subtract two numbers and return their difference.
3. To multiply two numbers and return their product.
4. To divide two numbers and return their quotient and print “Division by Zero” error if the denominator is zero.
5. Also add a docstring to describe the module. After creating module, import and execute functions.

Accepted Answer

> [!TLDR]
> Program 7-16 creates a user-defined **module**: a file `basic_math.py` holding four documented arithmetic functions (divide guards against zero), which a second program imports and executes.

**The idea — module creation and import.** Any `.py` file is a module. Placing related functions in one file gives them a shared, importable home; the triple-quoted string at the top becomes the module's **docstring**, retrievable as `basic_math.__doc__` or via `help(basic_math)`.

**Step 1 — create the module (save as `basic_math.py`):**

```python
# basic_math.py
"""basic_math - simple arithmetic on two numbers: add, subtract, multiply, divide."""

def add(x, y):
    """Return the sum of x and y."""
    return x + y

def subtract(x, y):
    """Return the difference x - y."""
    return x - y

def multiply(x, y):
    """Return the product of x and y."""
    return x * y

def divide(x, y):
    """Return x / y, or print an error if y is zero."""
    if y == 0:
        print("Division by Zero")
    else:
        return x / y
```

**Step 2 — import and execute the functions (a separate program in the same folder):**

```python
# use_basic_math.py
import basic_math

print(basic_math.__doc__)
print("Sum        :", basic_math.add(12, 4))
print("Difference :", basic_math.subtract(12, 4))
print("Product    :", basic_math.multiply(12, 4))
print("Quotient   :", basic_math.divide(12, 4))
basic_math.divide(12, 0)          # triggers the error message
```

**Expected output**

```
basic_math - simple arithmetic on two numbers: add, subtract, multiply, divide.
Sum        : 16
Difference : 8
Product    : 48
Quotient   : 3.0
Division by Zero
```

**Key points**
- `import basic_math` runs the module file once and makes its names available as `basic_math.add`, etc. …

Concept understanding — Module Creation And Import

Module Creation and Import

Why bother?

Creating a Module

Importing a Module

1. Import the entire module

2. Import specific items

3. Import with an alias

4. Import everything (avoid this)

How Python Finds Modules

The `name` Trick

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