Here is a beginners cheat sheet for Python programming language:
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Python Basics
Data Types
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Python has several data types including:
- Integers: Whole numbers, such as 1, 2, 3
- Floats: Decimal numbers, such as 1.0, 1.5, 3.14
- Booleans: True or False values
- Strings: A sequence of characters, such as “hello world”
- Lists: A collection of ordered elements, such as [1, 2, 3]
- Dictionaries: A collection of key-value pairs, such as {“name”: “John”, “age”: 30}
- Tuples: A collection of ordered, immutable elements, such as (1, 2, 3)
Variables
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In Python, variables can be assigned values using the = operator. For example:
codex = 5
y = "hello"
Printing Output
To print output in Python, use the print()
function. For example:
print("hello world")
Arithmetic Operators
Read more-Python Operators
Python supports common arithmetic operators, including:
+
addition-
subtraction*
multiplication/
division//
floor division%
modulus**
exponentiation
Comparison Operators
Python supports common comparison operators, including:
==
equal to!=
not equal to<
less than>
greater than<=
less than or equal to>=
greater than or equal to
Logical Operators
Python supports common logical operators, including:
and
logical ANDor
logical ORnot
logical NOT
Conditional Statements
Python supports if-else statements for conditional execution of code. For example:
if x > 10:
print("x is greater than 10")
else:
print("x is less than or equal to 10")
Loops
Python supports for and while loops for iterating over collections and executing code repeatedly. For example:
for i in range(10):
print(i)
while x < 10:
print(x)
x += 1
Functions
Read Also- Python Functions Functions in Python
Defining Functions
Functions can be defined in Python using the def
keyword. For example:
def square(x):
return x * x
Calling Functions
Functions can be called in Python by passing arguments to them. For example:
result = square(5)
print(result) # prints 25
File I/O
Opening Files
Files can be opened in Python using the open()
function. For example:
file = open("example.txt", "r")
Reading Files
Files can be read in Python using the read()
method. For example:
content = file.read()
print(content)
Writing to Files
Files can be written to in Python using the write()
method. For example:
file = open("example.txt", "w")
file.write("Hello world")
file.close()
Libraries
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Importing Libraries
Libraries can be imported in Python using the import
keyword. For example:
import math
Using Libraries
Libraries can be used in Python by calling their functions. For example:
result = math.sqrt(16)
print(result) # prints 4.0
Lists
Creating Lists
Lists can be created in Python using square brackets []
. For example:my_list = [1, 2, 3]
Accessing List Elements
List elements can be accessed using indexing, starting from 0. For example
print(my_list[0]) # prints 1
Modifying List Elements
List elements can be modified by assigning new values to them. For example:
my_list[0] = 4
print(my_list) # prints [4, 2, 3]
List Methods
Python provides many useful methods for working with lists, such as:
append()
: adds an element to the end of the listextend()
: adds elements from another list to the end of the listinsert()
: adds an element at a specific position in the listremove()
: removes the first occurrence of an element from the listpop()
: removes and returns the element at a specific position in the listindex()
: returns the index of the first occurrence of an element in the listcount()
: returns the number of times an element appears in the listsort()
: sorts the elements in the listreverse()
: reverses the order of the elements in the list
Dictionaries
Creating Dictionaries
Dictionaries can be created in Python using curly braces {}
. For example:
my_dict = {"name": "John", "age": 30}
Accessing Dictionary Elements
Dictionary elements can be accessed using keys. For example
print(my_dict["name"]) # prints "John"
Modifying Dictionary Elements
Dictionary elements can be modified by assigning new values to them. For example:
my_dict["age"] = 31
print(my_dict) # prints {"name": "John", "age": 31}
Dictionary Methods
Python provides many useful methods for working with dictionaries, such as:
keys()
: returns a list of all the keys in the dictionaryvalues()
: returns a list of all the values in the dictionaryitems()
: returns a list of all the key-value pairs in the dictionaryget()
: returns the value associated with a key, or a default value if the key is not foundpop()
: removes and returns the value associated with a keyupdate()
: updates the dictionary with key-value pairs from another dictionary
Classes
Creating Classes
Classes can be created in Python using the class
keyword. For example:
class Person: def __init__(self, name, age):
self.name = name self.age = age def greet(self): print("Hello, my name is", self.name)
Creating Objects
Objects can be created from classes using the class name and parentheses. For example:
person = Person("John", 30)
Accessing Object Attributes
Object attributes can be accessed using dot notation. For example:
print(person.name) # prints "John"
Calling Object Methods
Object methods can be called using dot notation and parentheses. For example
person.greet() # prints "Hello, my name is John"
That’s a quick overview of some of the basics of Python programming. There’s a lot more to learn, but this should give you a good starting point!
Control Flow
if-else Statements
The if-else
statement is used to conditionally execute code based on a boolean expression. For example
if x > 0:
print("x is positive")
else:
print("x is not positive")
for Loops
The for
loop is used to iterate over a sequence of elements. For example
for i in range(5):
print(i)
while Loops
The while
loop is used to repeatedly execute code while a boolean expression is true. For example:
i = 0
while i < 5:
print(i)
i += 1
break and continue Statements
The break
statement is used to exit a loop prematurely, while the continue
statement is used to skip over an iteration of a loop. For example:
for i in range(10):
if i == 5:
break
if i % 2 == 0:
continue
print(i)
Functions in Python for Beginners
Beginners can understood the basics of functions by the following topics:
Defining Functions
Functions are defined in Python using the def
keyword. For example:
def square(x):
return x * x
Calling Functions
Functions are called by their name followed by parentheses, with any arguments passed inside the parentheses. For example
print(square(3)) # prints 9
Default Arguments
Functions can have default argument values, which are used if an argument is not provided. For example:
def greet(name="World"):
print("Hello,", name)
greet() # prints "Hello, World" greet("John") # prints "Hello, John"
Variable Arguments
Functions can accept a variable number of arguments using the *args
syntax. For example:
def add(*args):
result = 0
for arg in args:
result += arg
return result
print(add(1, 2, 3)) # prints 6
Modules
Importing Modules
Modules can be imported in Python using the import
keyword. For example
import math
print(math.sqrt(4)) # prints 2.0
Alias Modules
Modules can be aliased using the as
keyword. For example
import math as m
print(m.sqrt(4)) # prints 2.0
Importing Functions from Modules
Individual functions can be imported from modules using the from ... import ...
syntax. For example:
from math import sqrt
print(sqrt(4)) # prints 2.0
Data Structures
Lists
Lists are a sequence of elements that can be accessed by their index. For example:
fruits = ["apple", "banana", "cherry"]
print(fruits[1]) # prints "banana"
Tuples
Tuples are like lists, but they are immutable, meaning that their values cannot be changed. For example:
point = (3, 4)
print(point[0]) # prints 3
Dictionaries
Dictionaries are collections of key-value pairs, which can be accessed by their keys. For example:
person = {"name": "John", "age": 30}
print(person["name"]) # prints "John"
Sets
Sets are collections of unique elements. For example:
fruits = {"apple", "banana", "cherry"}
fruits.add("apple")
print(fruits) # prints {"apple", "banana", "cherry"}
Object-Oriented Programming for beginners
OOP in Python for beginners are simply understood by following topics:
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Classes
Classes define objects with shared properties and methods. For example:
class Person:
def __init__(self, name, age):
self.name = name
self.age = age
def greet(self):
print("Hello, my name is", self.name) person = Person("John", 30)
person.greet() # prints "Hello, my name is John"
Inheritance
Inheritance allows classes to inherit properties and methods from parent classes. For example
class Student(Person):
def __init__(self, name, age, major): super().__init__(name, age) self.major = major def greet(self): super().greet()
print("I am studying", self.major)
student = Student("Jane", 20, "Computer Science")
student.greet() # prints "Hello, my name is Jane" followed by "I am studying Computer Science"
File Input/Output
Opening Files
Files can be opened using the open
function. For example:
file = open("example.txt", "r")
Reading Files
Files can be read using the read
function. For example
contents = file.read()
Writing to Files
Files can be written to using the write
function. For example
file.write("Hello, World!")
Closing Files
Files should be closed using the close
function. For example:
file.close()
That’s a quick overview of some of the more advanced features of Python for beginners. With these tools in your toolkit, you’ll be able to write powerful and flexible programs in Python!
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