Python: Functions Cheatsheet Part-1

 

Functions

A function is like a   mini ­program within a program that performs a specific task.

Why functions?

1. Creating a new function gives you an opportunity to name a group of statements, which makes your program easier to read, understand, and debug.
2. A major purpose of functions is to group code that gets executed multiple times. Without a function defined, you would have to copy and paste this code each time.

https://w3bigdata.blogspot.com/2024/03/python-if-ifelse-statement-with-examples.html

Common Built­in Functions:

● abs()

● help()

● min()

● max()

● hex() ­ hexadecimal representation of an integer

● bin() ­ binary

● oct() ­ octal

● id()

● input()

● int()

● float()

● str()

● print()

● bool()

● range()

● round()

● pow()

● sum()

● ord()

● len()

● type()

Common str methods:

● capitalize()

● count()

● encode()

● endswith()

● expandtabs()

● find()

● format()

● isalpha()

● isdigit()

● isdecimal()

● islower()

● isupper()

● join()

● startswith()

● swapcase()

● title()

User ­defined functions 

Definition of a function 

Syntax

def functionName(parameters) : statement(s)

● The keyword def introduces a function definition.

● It must be followed by the function name and the parenthesized list of formal parameters.

● There can be number of arguments in a function.

● The statements that form the body of the function start at the next line, and must be indented.

https://w3bigdata.blogspot.com/2024/03/python-data-types-complete-guide.html

Python if, if...else Statement With Examples

 

Step 1: The if Statement

The if statement is the basic form of control flow in Python. It allows for conditional execution of a statement or group of statements based on the value of an expression.

Step 2: The Condition

After the if keyword, you provide a condition. This condition is an expression that can be evaluated as True or False. Python will execute the body of the if only when the condition is True.

Step 3: The Body

If the condition is True, Python executes the block of code that's indented under the if statement. If the condition is False, the code block under the if is skipped.

Step 4: The else and elif Statements (Optional)

else:       You can follow an if statement with an optional else block which is executed when the if condition is False.

elif (else if):     It's used for multiple conditions to provide additional checks.

Example: Choosing a Path Based on Age

Imagine you're writing a program that suggests activities based on a person's age.

age = 18  # Let's assume the person is 18 years old

if age < 13:
    print("You can play in the kids' area.")
elif age < 18:
    print("You can join the teenagers' group.")
else:
    print("Welcome to the adults' zone.")

Explanation:

First condition (if age < 13): Python checks if age is less than 13. If True, it would print "You can play in the kids' area." Since our age is 18, this condition is False, so Python skips this block.

Second condition (elif age < 18): Next, Python checks if age is less than 18. Again, since our age is 18, this condition is also False, so Python skips this block too.

Else: Since none of the previous conditions were True, Python executes the code in the else block, printing "Welcome to the adults' zone.

Python Data Types - Complete Guide

 

 

A data type is a classification that specifies what type of value a variable has and what types of operations can be performed on it. Here's a list of the main data types in Python

1. Numbers:

Integers (int): 

Whole numbers, both positive and negative, without decimals. Like 3, -5, 42.

Floating-point numbers (float):

 Numbers with decimal points or in exponential form, such as 3.14, -0.001, or 2e2

2.  Text:

Strings (str): 

Text or characters. Anything inside quotes is a string, like "Hello!", "1234", or even "True".

3. Boolean:

Booleans (bool):

 Represents truth or falsehood. Only two possible values: True or False. Great for making decisions in your code.

4. Sequences: 

Lists (list): 

A list of items in an order. You can change the items (mutable). For example, [1, 'apple', True].

Tuples (tuple): 

Like a list, but you can't change it after making it (immutable). Useful for fixed data. Example: (1, 'banana', False).

5. Mappings:

Dictionaries (dict): 

Stores pairs of items as keys and values. Like a real dictionary with words and their meanings. Example: {'name': 'John', 'age': 30}.

6. Sets:

Sets (set):

 A collection of unique items, without order. Great for when you need to ensure no duplicates. Example: {1, 2, 3, 4}.

7. None Type:

None (NoneType): 

Special type representing the absence of a value, or "nothing". It's like saying a variable is empty or has no value.

Big Data - Hadoop (HDFS) File Blocks and Replication Factor

 

The Hadoop Distributed File System (HDFS) uses a block replication mechanism to ensure data reliability and availability across the cluster. Each file in HDFS is split into one or more blocks, and these blocks are stored on different DataNodes in the Hadoop cluster.

The replication factor is a configuration setting that determines the number of copies (replicas) of each block to be stored across different DataNodes. The default replication factor in HDFS is three, meaning that for every block of data, three copies are made and stored on three separate DataNodes.

Administrators can change the default replication factor according to the importance of the data and the storage capacity of the cluster. the replication factor in HDFS is a crucial parameter that impacts data reliability, availability, and storage efficiency in a Hadoop cluster.

HDFS Architecture with Example

 
HDFS

HDFS, or the Hadoop Distributed File System, is designed to store very large files across multiple machines in a large cluster of computers. Think of it as a way to store and access huge amounts of data by spreading it out over many computers, making it easier to handle and process big data. Let's break down the HDFS architecture into simpler terms and use an example to understand how it works.

Basic Components

HDFS has two main types of components:

1. NameNode: This is like the manager or directory of the system. The NameNode keeps track of where the pieces of your files are stored across the cluster. It doesn't store the actual data but has a map or index that tells which part of your data is on which computer.

2. DataNodes: These are the workers. Each DataNode stores a part of your data. Your big file is divided into smaller pieces (called blocks), and these blocks are stored on different DataNodes. This way, your data is spread across many machines.

Working Together

When you want to store a big file, the NameNode decides how to split the file into blocks and tells the DataNodes to store these blocks. If you want to access your file, the NameNode tells you which DataNodes have the parts you need, and then you can put the pieces together to get your file back.

Example

Imagine you have a very large photo album you want to keep in a library. The library (HDFS) decides to photocopy each photo (data block) and store each copy in different drawers (DataNodes) across several rooms (machines in the cluster). The catalog card (NameNode) doesn't hold the photos themselves but tells you exactly in which drawer and room you can find each photo. When you want to see your photo album, the library checks the catalog card and guides you to all the drawers in different rooms where the photos are kept. You can then collect the photocopies from each drawer to view your entire album.