Basics of Python for Data Science

This article helps you learn the fundamental and basic concepts of Python required for data science.

Python “Print()” function

In Python, to print any function we use the “print” keyword. For example: print("hello world"). The output will be “hello world”. There are some restrictions in the print function. In general, we use the “+” operator for the addition of two or more numbers, but in Python, we use the “+” operator for combining two or more strings. In Python, the print function “+” is called concatenation. For example: print(2+3) Output: 2+3. We can also print a string or any value by assigning it to a variable. For example:

example.py

hello = 'tim'
print(hello)

terminal

>> tim

Comments in Python

In Python, we usually comment sentences by using the “#” character. For example:

example.py

"""multiline comments
1. Add two number
2. Print their result
"""

a = 2 + 2
print(b) # output 4

Literal Constants

An example of a literal constant is a number like 5, 1.23, or a string like ‘This is a string’ or “It’s a string!”. It is called a literal because it is literal - you use its value literally. The number 2 always represents itself and nothing else - it is a constant because its value cannot be changed. Hence, all these are referred to as literal constants.

Numbers

In Python, there are mainly two types of numbers: integers and floats. An example of an integer is 1, 2, 100, etc. Examples of floating-point numbers (or floats for short) are 3.23 and 52.3E-4. The E notation indicates powers of 10. In this case, 52.3E-4 means 52.3 * 10^-4.

NOTE: IN PYTHON, THERE IS NO SEPARATE LONG TYPE; INTEGER CAN BE OF ANY SIZE.

Strings

A string is a sequence of characters. You can mention a string in single, double, or triple quotes. ‘hello’ or “hello” or ‘‘‘hello’’’. Using triple quotes indicates multiline strings.

Strings are immutable, i.e., once you have created a string, you cannot change it.

The format method

When we want to construct a string in a specific format we use the “format” method. For example:

example.py

age = 20
name = 'Swaroop'
print('{0} was {1} years old when he wrote this book'.format(name, age))
print('Why is {0} playing with that python?'.format(name))

terminal

>> Swaroop was 20 years old when he wrote this book
>> Why is Swaroop playing with that python?

Variable naming

There are some rules you have to follow for naming identifiers:
- The first character of the identifier must be a letter of the alphabet (uppercase ASCII or lowercase ASCII or Unicode character) or an underscore (_).
- The rest of the identifier name can consist of letters (uppercase ASCII or lowercase ASCII or Unicode character), underscores (_) or digits (0-9).
- Identifier names are case-sensitive. For example, myname and myName are not the same. Note the lowercase n in the former and the uppercase N in the latter.
- Examples of valid identifier names are i, name_2_3. Examples of invalid identifier names are 2things, this is spaced out, my-name, and >a1b2_c3.

Input of a variable

In C/C++, for taking input we use printf("") or cin commands. But in Python, we use input() keyword. For example:

example.py

name = int(input())

This is the input format for an integer type data. Similarly, we can also take input datatype for other datatypes.

We can also change the input format for being more precise.

example.py

name = int(input("Enter the input number: "))

Output: Enter the input number:

terminal

>> Enter the input number:

Operators and Expressions

Operators

Here is a quick overview of the available operators arranged according to their precedence order:

Operator	Description	Example	Result
**	Raises x to the power of y	3 ** 4	81
*	Multiplies the two numbers or repeats the string	2 * 3	6
/	Divides x by y	13 / 3	4.3333…
//	Divides x by y and rounds down to the nearest integer	13 // 3	4
%	Returns the remainder of the division	13 % 3	1
+	Adds two objects	3 + 5	8
-	Subtracts one number from the other	50 - 24	26
«	Shifts the bits of the number to the left	2 « 2	8
»	Shifts the bits of the number to the right	11 » 1	5
&	Bitwise AND of the numbers	5 & 3	1
^	Bitwise XOR of the numbers	5 ^ 3	6
\|	Bitwise OR of the numbers	5 \| 3	7
<	Checks if x is less than y	5 < 3	False
<=	Checks if x is less than or equal to y	3 <= 6	True
>	Checks if x is greater than y	5 > 3	True
>=	Checks if x is greater than or equal to y	4 >= 3	True
==	Compares if the objects are equal	2 == 2	True
!=	Compares if the objects are not equal	2 != 3	True
not	Boolean NOT	not True	False
and	Boolean AND	True and False	False
or	Boolean OR	True or False	True

These examples demonstrate the usage and behavior of each operator in Python.

Evaluation Order

When you have a set of operations in a single statement, which operation will you choose first to do? For example: 2 + 3 * 5 + (5 - 3) / 2

There is a sequence for the operations to be done.

Operator	Description
lambda	Lambda Expression
if - else	Conditional expression
or	Boolean OR
and	Boolean AND
not x	Boolean NOT
in, not in, is, is not, <, <=, >, >=, !=, ==	Comparisons, including membership tests and identity tests
\|	Bitwise OR
^	Bitwise XOR
&	Bitwise AND
«, »	Shifts
+, -	Addition and subtraction
*, /, //, %	Multiplication, Division, Floor Division, and Remainder
+x, -x, ~x	Positive, Negative, bitwise NOT
**	Exponentiation

In the next article, we will learn about control flow statements, functions, and modules.

For resources on how to understand and work with Python:

Comments

Load Comments