Introduction to Python

Introduction to Python


7 min read

Introduction to Python

Python is an interpreted, high-level, general-purpose programming language. Created by Guido van Rossum and first released in 1991, Python’s design philosophy emphasizes code readability with its notable use of significant whitespace. Since I am taking a course on introduction to python at the time of writing, what better way to document it than to write about it!? Btw, I’m gonna be trying to build a port scanner in python at the end of the course! (That will be a separate writeup hehe) So…lets get started!


  • To print basic text

    #Print string print("Hello, world!") print('Hello, world!')

  • To print multiline text

    print("""This string runs multiple lines dood!""")

  • To print 2 string concatenated together

    print("This string is "+"awesome!")

  • To add an empty line spacing in-between outputs

    #Print string print("Hello, world!") print('\n') #adds new line print('Hello, World!')


  • Basic operations

    #Math print(50 + 50) #addition print(50 - 50) #subtraction print(50 * 50) #multiplication print(50 / 50) #division

  • Advanced operations

    print(50 + 50 - 50 50 / 50) #pemdas print(50 * 2) #exponents print(50 % 6) #modulo print(50 // 6) #returns whole number

Variables & Methods

  • Declaring a variable and using it later in the program

    #Variables & Methods quote = "Control is an illusion" print(quote)

  • Using methods to modify the output

    print(quote.upper()) #uppercase print(quote.lower()) #lowercase print(quote.title()) #title print(len(quote)) #length of variable

  • Using methods to get properties/values of a certain type

    print(len(quote)) #length of variable
    name = "Neeranjan" #String age = 19 #int int(19) height = 1.8 #float float(1.8)
    print (int(age)) print (int(height))

  • Using methods to manipulate the output of text

    print("My name is " + name + "and I am " + str(age) + "years old. I am also " + str(height) + "m tall")

  • Increment variable by a certain amount

    age += 1 #increase age variable by 1 print(age) birthday = 1 #increase age variable by birthday variable age += birthday print(age)


  • Defining a function

    #Functions print("\nFunctions--") def whoAmI(): #This is a function name = "Neeranjan" #String age = 19 #int int(19) height = 1.8 #float float(1.8) print("My name is " + name + "and I am " + str(age) + "years old. I am also " + str(height) + "m tall")

  • Running a function


  • Adding parameters to a function

    #adding parameters def addOneHundred(num): print(num+100)


    #adding multiple parameters def addition(x,y): print(x + y)


    def multiply(x,y): return x * y #returning value to method != printing


    def squareRoot(x): print(int(x ** 0.5))


  • Creating functions to speed up simple yet time-consuming tasks

    def nl(): print('\n')


Boolean Expressions (T/F)

  • Creating basic Boolean expressions that will either return true or false

    #Boolean Expressions print("\nBoolean Expressions--") bool1 = True bool2 = 33 == 9 bool3 = False bool4 = 33 != 9 print(bool1, bool2, bool3, bool4) print(type(bool1))

  • Differentiating between STRING True and BOOLEAN

    #Boolean Expressions print("\nBoolean Expressions--") bool1 = True bool5 = "True" print(type(bool1)) print(type(bool5))

Relational and Boolean operators

  • Creating Boolean statements / Variables

    nl() #Relational and Boolean operators print("\nRelational and Boolean operators--") greaterThan = 7 > 5 lessThan = 5 < 7 greaterThanEqualTo = 7 >= 7 lessThanEqualto = 7 <=7 #All of the above statements will return True (boolean)

  • Creating statements with AND, OR & NOT

    testAnd = (7 > 5) and (5 < 7) #AND = true statement + true statement will make the whole thing return True testAnd2 = (7 > 5) and (5 > 7) #AND = true statement + false statement will make the whole thing return False

    testOr = (7 > 5) and (5 < 7) #OR = true statement + true statement will make the whole thing return True testOr2 = (7 > 5) and (5 > 7) #OR = true statement + false statement will make the whole thing return True

    testNot = not True #Returns False testNot2 = not False #Returns True

  • Refer to Truth table

Introduction to Python

Conditional Statements

  • Building a simple IF statement

    nl() #Conditional statements print("\nConditional statements--")

    def buyDrink(money): if money >= 2: return "You've got yourself a drink" else: return "No drink for you!"

    print(buyDrink(10)) print(buyDrink(1.5))

  • Building an advance IF statement with multiple conditions

    def buyBeer(age,money): if (age >= 21) and (money >= 5): return "Here is your cold beer!" elif (age >= 21) and (money < 5): return "Sorry you do not have enough money" elif (age < 21) and (money >= 5): return "Nice try, kid!" else: return "You're young, dumb and broke!"

    print(buyBeer(21,5)) print(buyBeer(20,4)) print(buyBeer(20,5))


  • Declaring a simple list and then printing it


    #Lists - Have brackets [] print("\nLists--")

    shows = ["Mr. Robot", "Money Heist", "Locke and key", "Orange is the new Black"]

    print(shows[0]) #Item one in a list is always 0 print(shows[1]) print(shows[0:3]) #Pulls out all values just b4 the last index print(shows[0:4]) #Pulls out all the values in the list print(shows[2:]) #Pulls out all the values after the index specified print(shows[:1]) #Pulls out all the values before the index specified / grabbing 1 item from the list print(shows[-1]) #Pulls out the last value in the list #print(len(shows)) #prints the number of items in the list

  • Adding to and removing from the list

    shows.append("Sex education") print(shows)

    shows.pop() #removes the last item in the list print(shows)

    shows.pop(0)#removed the first item in the list print(shows)


  • Declaring a tuple and printing it


    #Tuples - Does not change, () print("\nTuples--")

    grades = ("A", "B", "C", "D", "F") print(grades[1])


  • For loop


    #Looping print("\nLooping--")

    #For loops - start to finish of an iterate vegetables = ["cucumber", "spinach", "cabbage"]

    for x in vegetables: print(x)

  • While loop


    #While loops - Executes as long as true i = 1

    while i < 10: print(i) i += 1

Importing modules

  • Importing modules and using them in programs

    import sys #system function & parameters import os import datetime from datetime import datetime from datetime import datetime as dt #import with alias




#argv == $1 in bash.

#sys.exit() #exits python cleanly

Advance strings

  • Retrieve certain letters/words from certain word/sentence

    #Advance Strings print("\Advance Strings--") myName = "Neeranjan"

    print(myName[4]) #Retrieve a certain letter from the word print(myName[-1])

    sentence = "This is a sentence." print(sentence[:4]) #Retrieve a certain word from the sentence

  • Using the SPLIT and JOIN functions

    print(sentence.split()) #splits the sentence based on a delimiter

    splitSentence = sentence.split() joinSentence = ' '.join(splitSentence) #Joins the sentence back together using the provided delimiter. (space in this case) print(joinSentence)

  • Using quotes inside of a string variable

    quote = "He said, 'give me all your money'" quote1 = "He said, \"give me all your money\"" #both of these methods will work the same print(quote, quote1)

  • Stripping the extra space in a string

    tooMuchSpace = " hello " print(tooMuchSpace.strip())

  • Check for letter in word (case sensitive/non case sensitive)

    #case sensitive print("A" in "Apple") #True print("a" in "Apple") #False

    #non case sensitive letter = "A" word = "Apple"

    print(letter.lower() in word.lower())


  • A better way to print text with variables in it

    show = "Mr. Robot" show2 = "Orange is the new black" print("My favourite shows are {} and {}.".format(show, show2))


  • Declaring dictionary: assigning one value to a key (Key/Value Pairs)

    #Dictionaries - key/value pairs print("\Dictionary--")

    drinks = {"Orange Juice": 7, "Apple Juice": 10, "Lemon Juice": 8} #Drink = key; Price = value


  • Declaring dictionary: assigning multiple values to a key

    employees = {"Finance": ["Krista", "Susan", "Joanna"], "IT": ["Elliot", "Tyrell", "Darlene"], "HR": ["Leon", "Mr. Robot", "Phillip"]}


  • Adding new key : value pair to an existing dictionary

    employees["Legal"] = ["Trenton"] #Add new key:value pair print(employees)

    employees.update({"Sales": ["Anddy", "Ollie"]}) #Add new key:value pair print(employees)

  • Updating an existing value in a dictionary

    drinks["Orange Juice"] = 8 print(drinks)

  • Getting values from a dictionary


Introduction to Python