Program 7-3: Write a user defined function to add 2 numbers and display their sum.

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> [!TLDR]
> Program 7-3 defines the simplest kind of user-defined function — no parameters, no return value: `addnum()` inputs two numbers, adds them, and displays the sum; the definition does nothing until the function is *called*.

**The idea.** A user-defined function is created with `def`, a name, parentheses and an indented body. This first example deliberately keeps everything inside the function — input, processing and output — to show the *mechanics* of definition vs call.

```python
# Program 7-3: user defined function to add two numbers and display the sum

def addnum():
    fnum = int(input("Enter first number: "))
    snum = int(input("Enter second number: "))
    total = fnum + snum
    print("The sum of", fnum, "and", snum, "is", total)

# function call
addnum()
```

**Key lines**
- `def addnum():` — *defines* the function; Python just remembers the body, it does not run it.
- `addnum()` — the *call*; only now does control jump into the body, execute the three statements, and return to the line after the call.
- `int(input(...))` — `input()` returns a string; `int()` converts it so `+` performs arithmetic, not string concatenation. …

Set	Values	Average
A	80, 80, 80, 80	80
B	0, 80, 80, 160	80

Q.Program 7-3: Write a user defined function to add 2 numbers and display their sum.

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Q.Program 7-3: Write a user defined function to add 2 numbers and display their sum.

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