Python Cheatsheet

Table of Content

• Python Cheatsheet
  • Basics
    • Arithmetic Operations
    • Basic Data Types
    • Taking User Input
  • Strings
    • Creating String
    • String Concatenation
    • String Replication
  • Lists
    • Combine Two List
    • Nested List
    • Sorting List
    • Copy a List
  • Tuples
    • Convert Tuple to List
  • Sets
    • Creating a Set
    • Set Operations
  • Dictionaries
    • Creating Dictionaries
    • Dictionary Operations
  • Conditional Statements
    • If Statement
    • Elif Statement
    • Else Statement
  • Loops
    • While Loops
    • For Loop
  • Functions
    • Creating a Function
    • Calling Function
    • Passing Arguments
  • Lambda Functions

Basics

Arithmetic Operations

>>> 5 + 2   # Addition
7

>>> 4 - 3   # Subtraction
1

>>> 4 * 4   # Multiplication
16

>>> 10 / 2  # Division
5.0         # Return float value

>>> 10 // 2 # Division, but return integer value
5

>>> 10 % 2 # Modulas(Remainder)
0

>>> 2 ** 3 # Exponenet(Power)
8

Basic Data Types

Data Type	Example
Integer	-2,-1,0,1,2
Float	-1.5, -1.92, 2.25, 16.4
String	'python','is','love'
Complex	1j, 1+2j
Boolean	x = True, x = False

Taking User Input

input() function is used to take input from the user.

name = input("Enter Your Name:")
print("Hello " + name)

Strings

Creating String

 myString = "Python is easy!"

String Concatenation

A way to add two string together using “+” operator.

myString = "Python"
myString2 = "is easy"
ConString = myString + myString2
print(ConString)

Concatenating string and variable using , (comma).

no_of_apples = 20
print("We have", no_of_apples,"apples in a basket")
# OUTPUT: We have 20 apples in a basket*

String Replication

string = "Python" * 5
print(string)
# OUTPUT: PythonPythonPythonPythonPython

Lists

Lists are used to store the multiple items in a single variable. List are created using square brackets. List elements are changeable, can allow duplicate elements, and has defined order and that order will not change.Any new element will be placed at end of list. List index will start from 0 and will end at n-1 (where n is number of elements).

Creating List

lst = ["python","cpp","java"]

Fetching Values from List

>>> lst = ["python","cpp","java"]
>>> lst[0]
"python"
>>> lst[1]
"cpp"
>>> lst[2]
"java"

Adding Items to List

lst = [1,2,3]
lst.append(4)
print(lst)
# OUTPUT : [1, 2, 3, 4]

Method 2 insert() method is used to add item to specific index.

lst = [1,3,4]
# SYNTAX : .insert(index number, element)
lst.insert(1,2)
print(lst)
# OUTPUT : [1,2,3,4]

Removing Items from List

lst = [1,2,3,5]
lst.remove(5)
print(lst)
# OUTPUT : [1,2,3]

Combine Two List

lst1 = [1,2,3]
lst2 = ["x","y","z"]

combineList = lst1 + lst2
print(combineList)
# OUTPUT: [1, 2, 3, "x", "y", "z"]

Nested List

lst1 = [1,2,3]
lst2 = ["x","y","z"]
nestedList = [list1,list2]
print(nestedList)
# OUTPUT : [[1, 2, 3], ["x", "y", "z"]]

Sorting List

lst = [123,51,214,23,56]
lst.sort()
print(lst)
#OUTPUT : [23, 51, 56, 123, 214]

Copy a List

lst = ["a","b","c"]
lstcpy = lst.copy()
print(lstcpy)
# OUTPUT: ["a", "b", "c"]

Tuples

Tuples are similar to list. However, they are immutable and you can’t change the values stored in a tuple. Tuple are created using round brackets.

Creating Tuple

myTuple = (1,2,3,4)
print(myTuple)

Access Tuple Items You can access tuple items by referring to the index number.

myTuple = (1,2,3,4)
print(myTuple[2])
# OUTPUT: 3

Convert Tuple to List

Since Tuples are immutable. Instead we can convert tuple to list and can edit and then convert it back to tuple.

myTuple = (1,2,3)
convertedTuple = list(myTuple)
# Now we can edit the "convertedTuple" list.
convertedTuple[0] = 120
# Converting back to Tuple.
myTuple = tuple(ConvertedTuple)
print(myTuple)
# OUTPUT: (120,2,3)

Sets

Sets are used to store multiple items in a single variable. A Set is a collection which is both unordered and unindexed. Sets are written with curly brackets. Set cannot have two items with same value. A set can contain different data types.

Creating a Set

mySet = {"python", "java", "cpp"}
print(mySet)

Set Operations

Set with Different Data Types

mySet = {"python",142,True,"abc"}

Adding Element to Set

mySet = {1,2,3}
s.add(4)
print(s)
# OUTPUT: {1,2,3,4}

Adding Multiple Elements to Set

mySet = {1,2,3}
mySet.update([4,5,6,7])
print(mySet)
# OUTPUT : {1,2,3,4,5,6,7}

Dictionaries

Dictionaries are used to store data in pairs. A Pair contains key and value. It is ordered,changeable and cannot contain duplicate values. If duplicate values found then it will overwrite the values.

Creating Dictionaries

# SYNTAX

# dictionary_name = {
# "key_name" : "Value",
# "key2_name" : "Value2"
# }

dict = {
    "name" : "Van Rossum",
    "ID" : 1234,
    "year" : 1956
}

Dictionary Operations

Printing Items

print(dict["name"])

Length of Dictionary

print(len(dict))

# OUTPUT : 2

Adding Items

dict = {
    "name" : "Van Rossum",
    "ID" : 1234,
    "year" : 1956
}
# Adding Item
dict["profession"] = "Programmer"

Updating Item

# Syntax
# dict_name.update({"key":"value"})

dict.update({"ID":"9493"})

Print All Items Values

for i in dict:
    print(dict[i])

# OUTPUT:
#   Van Rossum
#   9493
#   1956

Conditional Statements

If Statement

If statement contains a logical expressions using which data is compared and a decision is made.

if expression:
    statements or code

Note : Indentation is required in IF statement

# Let's a create a program to check if person is eligible to vote or not

age = 15

if age < 18: # If age is less than 18 execute the block
    print("Not Eligible to Vote")

if age >= 18: # If age is greater than or equal to 18 execute the block
    print("Eligible to Vote")

# Here age is 15 so, 1st condition will be true and print the message.

Elif Statement

Elif keyword used if the previous if condition is false then it will execute the elif condition.

# Let's take the same example but using elif condition
age = 20

if age < 18:
    print("Not Eligible to Vote")

elif age >= 18:
    print("Eligible to Vote")

#OUTPUT: Eligible to Vote

Else Statement

else keyword is used if all previous condition becomes false then it execute the else block.

# Let us Understand using example of "If Number is +ve or -ve."

n = 0

if n > 0:
    print("N is +ve")

elif n < 0:
    print("N is -ve")

# In this case both the 'if' condition is false so we use 'else' block
else:
    print("N is Zero")

# OUTPUT: N is Zero

Loops

Loops are used when we want to execute same thing repeatedly until condition is not satisfied. For example, If we want to print “Hello World” 100 times, we will write print statement 100 times. We will use loop to achieve this.

While Loops

# print hello World 100 times

i = 1 
while i <= 100:
    print("Hello World")
    i=i+1

For Loop

# Same example but using for loop

# for i in range(101)-> range function is used instead of "i<=100" from while loop
# Syntax for range() function -> range(n-1), So If n=100, range will only include 99.

for i in range(101):
    print("Hello World")

Functions

Functions are block of code which only runs when it is called. Functions are defined using def keyword.

Creating a Function

SYNTAX

def function_name():
    code inside function

def my_function():
    print("Hello World")

Calling Function

def greeting():
    print("Good Morning")

# Calling Of Function
greeting()

Passing Arguments

# let us understand using example
# -> Take username and greet

# passing name argument
def greet(name):
    print("Hello " + name + ", Good Morning" )


greet("Rohan")

## Passing Two Arguments:

def greet(name, lastname):
    print("Hello " + name + lastname + ", Good Morning" )

greet("Rohan", "Kiratsata")

Lambda Functions

A lambda function is a small anonymous function means function without name.

SYNTAX

lambda arguments: expression

# Lambda function to square of number

n = lambda x : x*x

print(n(5))