## Order of Operations

• Consider the following expression 6 + 2 * -3
• Python language follows the same order of operations as in math world. You can remember order of operation by the acronym `PEMDAS`: Parenthesis first, exponential second, multiplication/division third and Addition/Subtraction fourth
``````6 + 2 * -3

6 - 6

0
``````
• Now if we write the expression
``````(6+2) * - 3

8 * -3
-24
``````
• Other expression `(100-5**3)/5`
``````(100-5**3)/5
(100 - 125)/5
-25/5
-5.0
``````
• Other expression `6 + 15 % 4`
``````6 + 15 % 4
6 + 3
9
``````
• Other expression ` 2 ** 2 + 24 // 4`
``````4 + 6
10
``````

## Spacing in Python

• In python, spaces after a number or symbol donot carry any mean. So 5**2 and 5 ** 2 both will give you result 25
• Spaces are meant to enhance readability, so space are generally encourage between operands & operators `5 ** 2`

## Number Types: Integers and Floats

• Add 5 to 3.14 => 8.14 (float) implicit conversion (5 is converted to float)
• Explicit conversion
``````x = 6.0
y = int(x)
``````

• Convert from int to float `float(6)`

## Complex Number Types

• Python inclues complex numbers as an official type
• Refer Here for complex math in python

• Comments are extra blocks of code that donot run. They are meant to clarify code for readers.
• In Python any text following # symbol on a single line is comment
``````# In this python file we will be calculating the area of circle
# We accept radius input from user

# Set the value of pi to a variable
pi = 3.14
area = pi * radius ** 2
``````
• Exercise: Write a program with decent comments to calculate area and perimeter of rectange. Take two inputs length and breadth
``````# This program calculates the area of rectangle

# input for length
length = float(input('Enter the length: '))

# calculate area

# calculate perimeter
perimeter = 2 * (length + breadth)

print(f"Area is {area} and perimeter is {perimeter}")
``````

## Docstrings

• Docstrings, are short for document strings.
• These state what a given document such as program, a function or a class actually does.
• The primary difference in syntax between docstring and comment is that docstrings are intended to be written over multiple lines which is accomplished with triple quotes
• Docstrings also help in creating a documentation for the document, class and functions
• Refer Here for the PEP about document strings
• Refer Here for PEP-8 styling guide for docstrings
• Refer Here for Google style guide for python
• Google has proposed docstring which are also widely adopted. Refer 3.8 section in google style guide Refer Here
• Refer Here for the sample class with docstrings

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