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Rohan Kiratsata

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# Python Cheat Sheet for Beginners

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This cheatsheet contains basic concepts of python, I will be uploading advanced concepts of python in Part 2.

# Python Cheatsheet for Beginners

Table of Content

## 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)
``````

### 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"
``````

``````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"}
``````

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

``````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
``````

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

# Credits

This cheatsheet is written and managed by Rohan Kiratsata.

Something is missing? Contribute to this repo and improve.

## Discussion (3)

Coder rudra

Nice

Sanjay

@rohankiratsata nice! π
I have added a little contribution to the repo.

Cheers!

Rohan Kiratsata

Thanks! I appreciate that. π