Introduction

1.2 What is PSF

The Python Software Foundation is an organisation devoted to advancing open source technology related to the Python programming language

1.3 Useful commands in python

>which python
>whereis python
>python --help
>echo $PATH
>python -V
>python --version
>export PATH=$PATH:/usr/local/bin

2. Python IDES

3. REPL

Python has interactive shell often known as REPL (Read Evaluate Print Loop). Example is given below.

4. Using Python as Calculator

Python can be used as simple calculator. Just type python in the terminal/command prompt. This will take you to the python console.
In the python console, any arithmetic calculation can be performed as given below

>>> 17 / 3  # int / int -> int
5
>>> 17 / 3.0  # int / float -> float
5.666666666666667
>>> 17 // 3.0  # explicit floor division discards the fractional part
5.0
>>> 17 % 3  # the % operator returns the remainder of the division
2
>>> 5 * 3 + 2  # result * divisor + remainder
17
 
** operator to calculate powers 

>>> 2 ** 7  # 2 to the power of 7
128

In interactive mode, the last printed expression is assigned to the variable _.
>>> tax = 12.5 / 100
>>> price = 100.50
>>> price * tax
12.5625
>>> price + _  # _ contains 12.5625 (last printed expression)
113.0625
>>> round(_, 2)
113.06

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