Arindam Dawn

Posted on Jun 22, 2020 • Edited on Jul 20, 2020 • Originally published at tabandspace.com

30 Days of Python 👨‍💻 - Day 2 - Data Types I

#python #challenge

Before diving deep into the nitty-gritty details of a programming language or perhaps even a human language, we need
to understand its terminologies and basic principles and start building a basic mental model which we can come back and
refer whenever needed.

The building block of any programming language can be divided mainly into the following:

Terminologies
Data Types
Actions (functions)
Best Practices

Today I spent understanding some basic Python terms, syntax, its data types and some of its actions or better known
as functions in programming terms.

Data Types

Data Types in simple words are a way to represent values. In our physical world, we have letters, numbers, symbols as
different type of commonly used values. Similarly, Python comprises of these fundamental data types:

int (to represent numbers)
float (to represent decimal numbers)
str (to represent strings)
bool (to represent boolean)
list
tuple
set
dict
complex (not used very often)
None (to represent an absence of value)

These are the standard data types available in Python. To create our own custom type, classes are used. Specialized data
types can also be used via importing external libraries or modules.

In contrast, in JavaScript, these are the following primitive types available:

number (for both whole and decimal numbers)
string
boolean
symbol
bigInt
null
undefined Also object as a non-primitive type.

Today I just spent time in understanding the number and string types of Python.

Numbers

There are 3 types of numeric data types:

int (stores whole numbers of unlimited size)
float (stores floating-point real number values)
complex (I just skipped it as of now as I learnt it is not used commonly, similarly to bigInt in JavaScript).

In contrast, JavaScript has two kinds of numeric data types, Number and BigInt.
The type function is used to determine the type of a value or an expression. (Similar to the typeof operator in
JavaScript)

    num = 100 # variable assignement
    print(type(num)) # <class 'int'>

    num2 = 99.99
    print(type(num2)) # <class 'float>

    expression1 = num * 10
    print(type(expression1)) # <class 'int'>

    expression2 = num + num2
    print(type(expression2)) # <class 'float'>

In Python, variable assignment happens by just writing a name and assigning a value using the = operator.
In JavaScript, a variable name needs to be preceded with var, const or let keyword.

Math functions

There are some built-in mathematical functions that allow us to calculate various mathematical operations with ease.
Math Functions and Constants - this document contains all the built-in
math functions and constants

    print(round(2.1)) # 2
    print(round(5.9)) # 6
    print(abs(-34)) # 34

Will explore the math module in detail some other day.

Variables

Variables store values. In python, these are the variable naming conventions:

Variables should start with a letter(preferrably lowercase) or underscore and can be followed by numbers or underscore
Snake case is the conventional way of writing variable with multiple words such as user_name (Javascript recommends cameCasing like userName)
They are case sensitive
Keywords should not overwrite keywords (Python keywords)

Strings

Strings in Python are an ordered sequence of characters (similar to Javascript).

    name = 'Python' # string assignment within single quotes
    name2 = "Python" # string assingment within double quotes
    name3 = '''This is a a very long string and supports 
            multiline statements as well''' # string assingment within 3 single quotes
    name4 = 'Hello! \"Rockstar Programmer\"' # string with escaped character sequence
    print(type(name)) # <class 'str'>
    print(type(name2)) # <class 'str'>
    print(type(name3)) # <class 'str'>
    print(type(name4)) # <class 'str'>

String Concatenation

Similar to Javascript, strings can be concatenated using the + operator. It simply joins or 'concatenates' strings.

    first_name = 'Mike'
    last_name = 'Tyson'
    print(first_name + ' ' + last_name) # Mike Tyson

Type Conversion

Unlike Javascript, where there is implicit type conversion (a.k.a Type Coercion), Python will throw an error if
operations are performed with different types

    user_name = 'John'
    age = 40
    print(user_name + age) # TypeError: can only concatenate str (not "int") to str
    # This would work in Javscript where it would convert the result to string type

In Python, types need to be converted explicitly to perform operations with different types

    user_name = 'John'
    age = 40
    print(user_name + str(age)) # John40
    print(type str(age)) # <class 'str'>

Similarly, strings can be converted into numbers

    lucky_number = 7
    lucky_number_stringified = str(7)
    lucky_number_extracted = int(lucky_number_stringified)
    print(lucky_number_extracted) # 7

That's all for today! Still taking it simple and easy. Will continue understanding the other string operations and built-in methods and functions along
with Boolean and List types. Pretty excited for Day 3!

Have a great one!

Top comments (17)

Adrian Mowat • Jun 25 '20

One thing I found strange about strings in Python is that there doesn’t seem to be much of a material difference between using single and double quotes. In other languages, string interpolation only works inside doubles and singles are treated as exact literals but strong formatting in python works differently (as I’m sure you’ll find soon). The only time I can see a need to choose one over the other is when you have quotes inside your strings. Maybe someone can correct me on this or point out the relevant idiom. Still, keep up the good work man. I waited to long to invest time in learning Python and I have to say it’s been a real joy since I started a few months ago.

Arindam Dawn • Jun 25 '20

After reading some articles and blog posts I found out that:

%-format method is a very old method for interpolation and is not recommended to use as it decreases the code readability.
In str.format() method we pass the string object to the format() function for string interpolation.
In the template method, we make a template by importing template class from built-in string module.
Literal String Interpolation method is powerful interpolation method which is easy to use and increase the code readability.

I am still figuring out the best practices but I personally like the f syntax.

And yes learning python is a real joy. Hope I keep getting better at it :) Thanks for reading the blog.

Adrian Mowat • Jun 26 '20

Yeah me too. f'{}...' usually meets my needs and I only use format when I need to use printf style formatting or the expression I want to print is complex enough to impact readability inside a simple interpolation.

I believe the %-format approach is from python2 and str.format() is preferred in python3. You still see it a lot though.

Fady khallaf • Jul 20 '20

"Variables must start with a lowercase letter" can you edit this line because Python variables can start with uppercase letters as well. the variable in python must start with a letter or underscore (letter can be a capital uppercase or lowercase), it can't start with a number or special character.