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When working with Python, you need an environment where your code can execute. Windows provides Command Prompt and PowerShell, each with different capabilities.

Command Prompt (cmd): Supports only built-in Windows commands.
PowerShell: More powerful; supports scripting, advanced commands, and works like Linux/macOS terminals.

Both can run Python through the command:

python

This starts Python IDLE (REPL mode) — an interactive shell where Python executes your commands immediately.

Example:

>>> print("Hello")
Hello

Airthmetic Operations

Python supports the standard arithmetic operators. Below each operator is explained and illustrated with examples and expected output.

Subtraction `-`

>>> 9 - 8
1

Subtracts the right-hand operand from the left-hand operand.

True division `/` (returns `float`)

The division operator / always returns a float even if both operands are integers.

>>> 8 / 4
2.0
>>> 5 / 2
2.5

This is useful because division can produce non-integer results; returning a float preserves precision.

Floor (integer) division `//`

Use // if you want only the integer part (the quotient) and to discard any fractional remainder.

>>> 10 // 3
3
>>> -7 // 3
-3  # floor division rounds toward negative infinity

Note: with negative numbers // performs floor division — results may look unintuitive if you expect truncation toward zero.*

Exponentiation `**`

>>> 2 ** 3
8
>>> 4 ** 0.5
2.0  # square root

Raises the left operand to the power of the right operand.

Operator precedence and parentheses

Python obeys the usual mathematical rules (BODMAS). Use parentheses to change order.

Python IDE

>>> 8 + 2 * 3
14
>>> (8 + 2) * 3
30

Common pitfall: incomplete expressions cause syntax errors:

>>> 8 + 9 -
SyntaxError: invalid syntax

Using the Underscore `_` in Python IDLE

In Python, the underscore _ is a special built-in name that automatically stores the result of the last executed expression. This allows you to reuse the previous output without retyping it, making calculations faster and more convenient.

Example1:

>>> 10 + 5
15

>>> _ * 2
30

Explanation:

After evaluating 10 + 5, Python stores the result (15) in _.
When you enter _ * 2, Python uses the stored value (15) and performs: 15 × 2 = 30

Example1:

>>> 50 // 3
16

>>> 1 + _
17

Python automatically uses the last result (16) and adds 1.

Variables in Python

A variable is a name used to store a value in memory. Python creates variables automatically when a value is assigned.

Example:

x = 2
print(x + 3)     # Output: 5

y = 3
print(x + y)     # Output: 5

Variables are mutable

Values of variables can be changed easily:

x = 9
print(x)        # 9
print(x + y)    # 12

Assigning expressions to variables

When you assign a value, nothing is printed unless you use print().

num_one = 8**3
# No output
print(num_one)
# 512

Summary

Python IDLE can be accessed by typing python in Command Prompt or PowerShell.
Python supports standard arithmetic operators: +, -, *, /, //, %, **.
/ returns a float, while // gives the integer (floor) result.
Python follows BODMAS, and parentheses can override precedence.
In IDLE, _ stores the result of the previous expression for reuse.
Variables store values for later use, and results appear only when using print() statement.

Written By: Muskan Garg

Python IDLE and Exploring Number Operations