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!
Strings
To print basic text
#!/bin/python3
#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
#!/bin/python3
#Print string print("Hello, world!") print('\n') #adds new line print('Hello, World!')
Math
Basic operations
#!/bin/python3
#Math print(50 + 50) #addition print(50 - 50) #subtraction print(50 * 50) #multiplication print(50 / 50) #divisionAdvanced 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
#!/bin/python3
#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)
Functions
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
whoami()
Adding parameters to a function
#adding parameters def addOneHundred(num): print(num+100)
addOneHundred(50)
#adding multiple parameters def addition(x,y): print(x + y)
addition(50,55)
def multiply(x,y): return x * y #returning value to method != printing
print(multiply(5,5))
def squareRoot(x): print(int(x ** 0.5))
squareRoot(64)
Creating functions to speed up simple yet time-consuming tasks
def nl(): print('\n')
nl()
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
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))
Lists
Declaring a simple list and then printing it
nl()
#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)
Tuples
Declaring a tuple and printing it
nl()
#Tuples - Does not change, () print("\nTuples--")
grades = ("A", "B", "C", "D", "F") print(grades[1])
Looping
For loop
nl()
#Looping print("\nLooping--")
#For loops - start to finish of an iterate vegetables = ["cucumber", "spinach", "cabbage"]
for x in vegetables: print(x)
While loop
nl()
#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
print(sys.version)
print(datetime.now())
print(dt.now())
#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))
Dictionary
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
print(drinks)
Declaring dictionary: assigning multiple values to a key
employees = {"Finance": ["Krista", "Susan", "Joanna"], "IT": ["Elliot", "Tyrell", "Darlene"], "HR": ["Leon", "Mr. Robot", "Phillip"]}
print(employees)
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
print(employees.get("IT"))