Cheatsheets are good when you want to revise some of the concepts but not an idle way to start learning. Theory Python is a scripting language. - Language like c++/java's code needs to be compiled by its compiler. After compilation, it is just machine-level code. Whereas in a scripting language, its interpreter will be run the code on the spot one line at a time. Scripting vs. Compiled? VSCODE extension: Python Python for vscode Magic Python Arepl Making a virtual env: Why Virtual env? Because managing python dependencies is a mess, this will install dependencies for that project only instead of globally. this will create a venv folder in your directory. python -m venv venv this will activate this virtual env. source ./venv/bin/activate Comments in python single-line use # # single line comments multiline use . often called as docstring, as it is just to document function/classes. ''' '''
This is a example of 
Multiline comment.
''' Data Types: int # Whole Numbers float # Number with decimals. str # String list # ordered sequence of object dict # unordered key-value pairs. tup # ordered immutable seq. of objects. set # Unordered collection of unique objs. bool # Logical value True / False. None # no value Naming conventions: Use underscore for variables. variables cannot Start with a number. Avoid special meaning keywords. Use snake case for functions. Use CamelCase for Classes names. Printing in Python: print("") Numbers in Python: print(1+2) # Addition
print(3-2) # Subtraction
print(3*2) # Multiplication
print(3/2) # Division
print(3%2) # Mod.
print(3**2) # Power
print((3 + 10) * 15) # Using Braces. Using with variables: a = 10
print(a)
# TO check the type:
print(type(a)) Variables make it easy to understands the code. my_income = 100
tax_rate = 0.1
my_taxes = my_income*tax_rate
print("My income tax is",my_taxes) Strings in Python: String is nothing but ordered seq. of characters.
Note: Strings are immutable Using directly with print: print("Simple String")
print('Add quotes inside the  "string" by using single quote.')
print("concat string "+"like this") Taking Input greeting = "Hello"
name = input("Enter your name: ")
print(greeting + ' ' + name) Use instead of This will auto seprate them by spaces. , + print(greeting,name) Escape characters in python: print("Hello\nWorld")
# or
print("""
 ---
Hello
world\
Yeahh!!
"Quotes"
'Single quote'
 ---
""") Check the length of the string: print(len("Hey")) String indexing a = "Hello"
a[0] Will return H String Slicing a[start:end:step]
a[0:2] # Start from 0th index till 2(excluding)
a[::2] # Step will be 2.
# We can use this to print a string backwards
s[::-1] String methods: # Multiply Strings
a = 'H' * 10 # Upper Case a string
s.upper() # Lower case
s.lower() # Splitting
s.split('W')
s.split() # split via whitespace. Formatting strings: .format() F-string f"" print('The {2} {1} {0}'.format('fox','brown','quick'))
print('First Object: {a}, Second Object: {b}, Third Object: {c}'.format(a=1,b='Two',c=12.3))
num = 23.45
print("My 10 character, four decimal number is:{0:10.4f}".format(num))
print(f"My 10 character, four decimal number is:{num:10.4f}") String Print alignment left_alignment = "Left Text"
center_alignment = "Centered Text"
right_alignment = "Right Text"
print(f"{left_alignment : <20}|{center_alignment : ^15}|{right_alignment : >20}")
More about this: https://pyformat.info/ Lists in Python: Basic Usage # Supports dynamic types, as it is python :)
my_list = [100,2.5,"Mohit"]
# len(my_list) for length
# Change objs:
my_list[0]=1000 Slicing is same as String slicing Concat a = [1,2,3]
b = [4,5]
c = a + b Append the list my_list.append(10.8) Poping objs my_list.pop(index) # default index is -1, returns popped element. Sorting a = [1,2,3]
a.sort() # in-place sort, it will modify the list, returns None
# Tip: use sorted(a) it will return the value instead of in-place Reverse a = [1,2,3]
a.reverse() # also in-place Nested list a = [1, 2, 3, [4,5,]]
print(a[3][1]) # Returns 5. Dictionaries in Python Unordered key-value mappings, basically you can have custom keys
</br>Think it like, you can use this to make dynamic variables, where key will be the variable name.
</br>Like list value can be any data type. Basic Usage prices = {"apple":10, "orange":20.5}
print(prices)
print(prices["apple"])
print(prices.keys()) # get keys
print(prices.values()) # get values
print(prices.items()) # get items, return tuples with keys and values
print(prices.pop("apple")) # Pop the object
print(prices)
print(prices.clear()) # Clear All
print(prices)
print(prices.get("banana")) # it will check if it is present, return None if not.
print(prices.__contains__("apple")) # Returns true/false Tuples in Python Same as a list, but immutable. Basic Usage a = (1,2,2,4)
print(a)
# Interesting Fact: tuple supports only two methods:
a.count(2) # This can be use with list as well.
a.index(3) # This can be use with list as well. Sets in Python Sets are an unordered collection of unique elements. a = set()
a.add(1)
a.add(1)
a.add(1)
print(a) # {1} Convert list to set a = [1,1,2,2,2,3,3,3]
a = set(a) File IO with Python init file obj file = open("file.txt") read contents contents = file.read()
print(contents) move the cursor/pointer file.seek(0) read line by line contents = file.readlines() # returns list of lines. close the file file.close() Using context manager with open("file.txt") as file:
    print(file.read()) different modes for file : Read r : Read and Write r+ : Write (will override the file) w : Write + Read (will override the file) w+ : Append the file a Chaining comparison operators: To chain these operators, we have these logical operators ==, != <, >, >=, <= and is and or not if 2 > 3 and 2 > 5:
    print("I am inevitable")
if "hello" is "world" or "india" is "country":
    print("Yeah!!")
if not 10 == 10:
    print("Tough luck!" ) Python Statements: Indentation is in python. important if, elif, else loc = 'Bank'

if loc == 'Auto Shop':
    print('Welcome to the Auto Shop!')
elif loc == 'Bank':
    print('Welcome to the bank!')
else:
    print('Where are you?') for loops # iterate list/string/tuple
l = [1,2,3]
for item in l:
    print(item)
# extraction made easy
list2 = [(2,4),(6,8),(10,12)]
for t1,t2 in list2: # Same as dict. t1 will be key, t2 will be value.
    print(t1) # will print 2,6,10
# Protip about dict: use .value() and .keys() for looping Values/keys. white loops in python we can use python with else statement. x = 1
while x < 3:
    print(f"x is {x}")
    x = x + 1
else:
    print("Uhhoo! x > 3") Statement in python : Breaks out of the current closest enclosing loop. break : Goes to the top of the closest enclosing loop. continue : Does nothing at all, Programmers use this for placeholder. pass def future_method():
    # Todo: implement it later.
    pass
while True:
    break
for i in range(10):
    if i == 5:
        #omit
        continue 
    print(i) Some useful operators range() range is a generator.
<br/> : <br/>
Use directly with loops for iteration. Syntax range(start,end,step) a = list(range(0,11,2)) # returns 0,2,4,..10 enumerate() with help of this we can keep track of index and value. a = [20,100,5,3,6]
for index,value in enumerate(a):
    print(f"{index}\t{value}") zip() zip multiple lists.
a = [1,2,3]
b = [4,5,6]
for item in zip(a,b):
    print(item) in operator: a = [1,2,3]
print(3 in a) # True min and max: a = [1,2,3]
print(min(a)) # 1
print(max(a)) # 3 List Comprehensions Quicker and unique way to create lists. # Grab every letter in string
lst = [x for x in 'word']

# Square numbers in range and turn into list
lst = [x**2 for x in range(0,11)]

# Check for even numbers in a range
lst = [x for x in range(11) if x % 2 == 0] help function in python if you are lazy like me, want to learn documentation about specific inbuilt method via terminal, you can use help() a = [1,2,3]
help(a.insert) # will print info about this method Functions in python Basic function with argument and default value # def keyword to define functions.
def say_hello(name="world"):
    print(f"Hello {name}!")
    # or return f"Hello {name}!" if you want to return it. *args and **kwargs : N number of arguments, returns tuple. *args : N number of keyword arguments, returns dict. **kwargs def total_income(*args, **kwargs):
    print(f"Income for month, {kwargs['month']} is : {sum(args)}")
total_income(10,20,300,month="July") lamda, filter and map #map
def square(num):
    return num**2
my_nums = [1,2,3,4,5]
map(square,my_nums) # 1, 4, 9, 16, 25

# filter
def check_even(num):
    return num % 2 == 0
nums = [0,1,2,3,4,5,6,7,8,9,10]
filter(check_even, nums) # 0, 2, 4, 6, 8, 10

# lets convert each of the above function to lambda.
map(lambda num:num**2,my_nums)
filter(lambda num:num%2==0, nums) Classes in python Basic implementation class Circle:
    pi = 3.14

    # Circle gets instantiated with a radius (default is 1)
    def __init__(self, radius=1):
        self.radius = radius 
        self.area = radius * radius * Circle.pi

    # Method for resetting Radius
    def setRadius(self, new_radius):
        self.radius = new_radius
        self.area = new_radius * new_radius * self.pi

    # Method for getting Circumference
    def getCircumference(self):
        return self.radius * self.pi * 2


c = Circle()

print('Radius is: ',c.radius)
print('Area is: ',c.area)
print('Circumference is: ',c.getCircumference()) Inheritance class Animal:
    def __init__(self):
        print("Animal created")

    def whoAmI(self):
        print("Animal")

    def eat(self):
        print("Eating")


class Dog(Animal):
    def __init__(self):
        Animal.__init__(self)
        print("Dog created")

    def whoAmI(self):
        print("Dog")

    def bark(self):
        print("Woof!") Polymorphism class Animal:
    def __init__(self, name):    # Constructor of the class
        self.name = name

    def speak(self):              # Abstract method, defined by convention only
        raise NotImplementedError("Subclass must implement abstract method")


class Dog(Animal):
    
    def speak(self):
        return self.name+' says Woof!'
    
class Cat(Animal):

    def speak(self):
        return self.name+' says Meow!'
    
fido = Dog('Fido')
isis = Cat('Isis')

print(fido.speak())
print(isis.speak()) Using Special methods Just like we have more special methods. __init__ class Book:
    def __init__(self, title, author, pages):
        print("A book is created")
        self.title = title
        self.author = author
        self.pages = pages

    def __str__(self):
        return "Title: %s, author: %s, pages: %s" %(self.title, self.author, self.pages)

    def __len__(self):
        return self.pages

    def __del__(self):
        print("A book is destroyed")


book = Book("Python Rocks!", "Jose Portilla", 159)

#Special Methods
print(book)
print(len(book))
del book Exception Handling try, except, finally, and else. def askint():
    while True:
        try:
            val = int(input("Please enter an integer: "))
        except:
            # You can also expect specific error like TypeError or generic type Exception
            print("Looks like you did not enter an integer!")
            continue
        else:
            print("Yep that's an integer!")
            break
        finally:
            print("Finally, I executed!")
        print(val) Decorators def new_decorator(func):

    def wrap_func():
        print("Code would be here, before executing the func")

        func()

        print("Code here will execute after the func()")

    return wrap_func

@new_decorator
def func_needs_decorator():
    print("This function is in need of a Decorator")

func_needs_decorator()
# Code would be here, before executing the func
# This function is in need of a Decorator
# Code here will execute after the func() Generators # Without generator
def get_me_cubes(n):
    output_list = []
    for i in range(n):
        output_list.append(i**3)
    return output_list

print(get_me_cubes(10))
# With generator
def generate_cubes(n):
    for i in range(n):
        yield i**3

print(generate_cubes(10)) Useful Python modules you should look. collections os shutil datetime math random pdb re timeit zipfile Working with CSVs in python # don't forget to install csv
import csv
data = open('example.csv',encoding="utf-8")
# passing encoding is important otherwise you will get the Unicode error.
csv_data = csv.reader(data)
# reading
data_lines = list(csv_data)
# writing 
file_to_output = open('to_save_file.csv','w',newline='')
# use 'a' for append
csv_writer = csv.writer(file_to_output,delimiter=',')
csv_writer.writerow(['a','b','c'])
file_to_output.close() Working with pdfs in python # don't forget to use PyPDF2
import PyPDF2
f = open('Working_Business_Proposal.pdf','rb')
# we need to pass rb for binary files.
pdf_text = []

pdf_reader = PyPDF2.PdfFileReader(f)

for p in range(pdf_reader.numPages):
    page = pdf_reader.getPage(p)
    pdf_text.append(page.extractText()) Sending Emails with python import smtplib
smtp_object = smtplib.SMTP('smtp.gmail.com',587)
email = "youremail@email.com"
password = "yourpassword"
# Tip: search about how you generate app passwords.
smtp_object.login(email,password)
from_address = "fromemail@email.com"
to_address = "toemail@email.com"
subject = "Subject"
message = "Message"
msg = "Subject: " + subject + '\n' + message
smtp_object.sendmail(from_address,to_address,msg)
smtp_object.quit() That’s it. I would recommend you to learn in-depth from this course: Udemy Course If you can self learn, then you can refer to this Repository: Github

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