Let's start with the first Python Concept today

1. Data Structures

Before you analyze anything, you need to organize and store your data properly. Python offers four main data structures that every data analyst must master.

*Lists ([])*
A list is an ordered collection of items that can be changed (mutable).

*Example* :

scores = [85, 90, 78, 92]
print(scores[0]) # Output: 85

Use lists to store rows of data, filtered results, or time-series points.

*Tuples (())*
Tuples are like lists but immutable — once created, they can't be modified.

*Example* :

coords = (12.97, 77.59)

Use them when data should not change, like a fixed location or record.

*Dictionaries* ({})
Dictionaries store data in key-value pairs. They’re extremely useful when dealing with structured data.

Example:

person = {'name': 'Alice', 'age': 30}
print(person['name']) # Output: Alice

Use dictionaries for JSON data, mapping columns, or creating summary statistics.

*Sets (set())*
Sets are unordered collections with no duplicate values.

Example:

departments = set(['Sales', 'HR', 'Sales'])
print(departments) # Output: {'Sales', 'HR'}

Use sets when you need to find unique values in a dataset.

*Here are some important points to remember:*

- Lists help you store sequences like rows or values from a column.

- Dictionaries are great for quick lookups and mappings.

- Sets are useful when working with unique entries, like distinct categories.

- Tuples protect data from accidental modification.


*You’ll use these structures every day with pandas. For example, each row in a DataFrame can be treated like a dictionary, and columns often act like lists.*

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🔰 Deep Python Roadmap for Beginners 🐍

Setup & Installation 🖥⚙️
• Install Python, choose an IDE (VS Code, PyCharm)
• Set up virtual environments for project isolation 🌎

Basic Syntax & Data Types 📝🔢
• Learn variables, numbers, strings, booleans
• Understand comments, basic input/output, and simple expressions ✍️

Control Flow & Loops 🔄🔀
• Master conditionals (if, elif, else)
• Practice loops (for, while) and use control statements like break and continue 👮

Functions & Scope ⚙️🎯
• Define functions with def and learn about parameters and return values
• Explore lambda functions, recursion, and variable scope 📜

Data Structures 📊📚
• Work with lists, tuples, sets, and dictionaries
• Learn list comprehensions and built-in methods for data manipulation ⚙️

Object-Oriented Programming (OOP) 🏗👩‍💻
• Understand classes, objects, and methods
• Dive into inheritance, polymorphism, and encapsulation 🔍

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SQL vs Python

SQL is great for managing and querying structured databases, especially when dealing with large datasets. It excels in tasks like filtering, sorting, and aggregating data.

Python, on the other hand, is a versatile programming language used for a broader range of tasks. In the context of data, Python is powerful for data manipulation, analysis, and machine learning. It offers libraries like Pandas for data manipulation, NumPy for numerical operations, and Scikit-Learn for machine learning.

In summary, SQL is essential for efficient database querying, while Python provides a more comprehensive solution for various data-related tasks, making them often used together in data-related workflows.

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Data Scientist Roadmap
|
|-- 1. Basic Foundations
| |-- a. Mathematics
| | |-- i. Linear Algebra
| | |-- ii. Calculus
| | |-- iii. Probability
| | `-- iv. Statistics
| |
| |-- b. Programming
| | |-- i. Python
| | | |-- 1. Syntax and Basic Concepts
| | | |-- 2. Data Structures
| | | |-- 3. Control Structures
| | | |-- 4. Functions
| | | `-- 5. Object-Oriented Programming
| | |
| | `-- ii. R (optional, based on preference)
| |
| |-- c. Data Manipulation
| | |-- i. Numpy (Python)
| | |-- ii. Pandas (Python)
| | `-- iii. Dplyr (R)
| |
| `-- d. Data Visualization
| |-- i. Matplotlib (Python)
| |-- ii. Seaborn (Python)
| `-- iii. ggplot2 (R)
|
|-- 2. Data Exploration and Preprocessing
| |-- a. Exploratory Data Analysis (EDA)
| |-- b. Feature Engineering
| |-- c. Data Cleaning
| |-- d. Handling Missing Data
| `-- e. Data Scaling and Normalization
|
|-- 3. Machine Learning
| |-- a. Supervised Learning
| | |-- i. Regression
| | | |-- 1. Linear Regression
| | | `-- 2. Polynomial Regression
| | |
| | `-- ii. Classification
| | |-- 1. Logistic Regression
| | |-- 2. k-Nearest Neighbors
| | |-- 3. Support Vector Machines
| | |-- 4. Decision Trees
| | `-- 5. Random Forest
| |
| |-- b. Unsupervised Learning
| | |-- i. Clustering
| | | |-- 1. K-means
| | | |-- 2. DBSCAN
| | | `-- 3. Hierarchical Clustering
| | |
| | `-- ii. Dimensionality Reduction
| | |-- 1. Principal Component Analysis (PCA)
| | |-- 2. t-Distributed Stochastic Neighbor Embedding (t-SNE)
| | `-- 3. Linear Discriminant Analysis (LDA)
| |
| |-- c. Reinforcement Learning
| |-- d. Model Evaluation and Validation
| | |-- i. Cross-validation
| | |-- ii. Hyperparameter Tuning
| | `-- iii. Model Selection
| |
| `-- e. ML Libraries and Frameworks
| |-- i. Scikit-learn (Python)
| |-- ii. TensorFlow (Python)
| |-- iii. Keras (Python)
| `-- iv. PyTorch (Python)
|
|-- 4. Deep Learning
| |-- a. Neural Networks
| | |-- i. Perceptron
| | `-- ii. Multi-Layer Perceptron
| |
| |-- b. Convolutional Neural Networks (CNNs)
| | |-- i. Image Classification
| | |-- ii. Object Detection
| | `-- iii. Image Segmentation
| |
| |-- c. Recurrent Neural Networks (RNNs)
| | |-- i. Sequence-to-Sequence Models
| | |-- ii. Text Classification
| | `-- iii. Sentiment Analysis
| |
| |-- d. Long Short-Term Memory (LSTM) and Gated Recurrent Units (GRU)
| | |-- i. Time Series Forecasting
| | `-- ii. Language Modeling
| |
| `-- e. Generative Adversarial Networks (GANs)
| |-- i. Image Synthesis
| |-- ii. Style Transfer
| `-- iii. Data Augmentation
|
|-- 5. Big Data Technologies
| |-- a. Hadoop
| | |-- i. HDFS
| | `-- ii. MapReduce
| |
| |-- b. Spark
| | |-- i. RDDs
| | |-- ii. DataFrames
| | `-- iii. MLlib
| |
| `-- c. NoSQL Databases
| |-- i. MongoDB
| |-- ii. Cassandra
| |-- iii. HBase
| `-- iv. Couchbase
|
|-- 6. Data Visualization and Reporting
| |-- a. Dashboarding Tools
| | |-- i. Tableau
| | |-- ii. Power BI
| | |-- iii. Dash (Python)
| | `-- iv. Shiny (R)
| |
| |-- b. Storytelling with Data
| `-- c. Effective Communication
|
|-- 7. Domain Knowledge and Soft Skills
| |-- a. Industry-specific Knowledge
| |-- b. Problem-solving
| |-- c. Communication Skills
| |-- d. Time Management
| `-- e. Teamwork
|
`-- 8. Staying Updated and Continuous Learning
|-- a. Online Courses
|-- b. Books and Research Papers
|-- c. Blogs and Podcasts
|-- d. Conferences and Workshops
`-- e. Networking and Community Engagement

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Python Variables: How to Define/Declare String Variable Types

What is a Variable in Python?
A Python variable is a reserved memory location to store values. In other words, a variable in a python program gives data to the computer for processing.

Python Variable Types
Every value in Python has a datatype. Different data types in Python are Numbers, List, Tuple, Strings, Dictionary, etc. Variables in Python can be declared by any name or even alphabets like a, aa, abc, etc.

How to Declare and use a Variable
Let see an example. We will define variable in Python and declare it as “a” and print it.

1 a=100
2 print (a)

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Essential NumPy Functions for Data Analysis

Array Creation:

np.array() - Create an array from a list.

np.zeros((rows, cols)) - Create an array filled with zeros.

np.ones((rows, cols)) - Create an array filled with ones.

np.arange(start, stop, step) - Create an array with a range of values.


Array Operations:

np.sum(array) - Calculate the sum of array elements.

np.mean(array) - Compute the mean.

np.median(array) - Calculate the median.

np.std(array) - Compute the standard deviation.


Indexing and Slicing:

array[start:stop] - Slice an array.

array[row, col] - Access a specific element.

array[:, col] - Select all rows for a column.


Reshaping and Transposing:

array.reshape(new_shape) - Reshape an array.

array.T - Transpose an array.


Random Sampling:

np.random.rand(rows, cols) - Generate random numbers in [0, 1).

np.random.randint(low, high, size) - Generate random integers.


Mathematical Operations:

np.dot(A, B) - Compute the dot product.

np.linalg.inv(A) - Compute the inverse of a matrix.

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Roadmap to become a Python Developer:

📂 Learn Python Basics (Syntax, Data Types, Loops)
∟📂 Learn Data Structures (Lists, Tuples, Dicts, Sets)
∟📂 Learn Functions & Modules
∟📂 Learn File Handling & Exceptions
∟📂 Learn OOP Concepts
∟📂 Learn Libraries (Pandas, NumPy, etc.)
∟📂 Learn Web Development (Flask / Django)
∟📂 Learn APIs & Database Integration
∟📂 Build Projects & Portfolio
∟✅ Apply for Job

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9 tips to improve your code:

- Declare variables close to usage
- Functions do 1 thing
- Avoid long functions
- Avoid long lines
- Don't repeat code
- Use descriptive variable/function names
- Use few arguments
- Simplify conditions (return age >17;)
- Remove unused code

Without errors, No-one can become a good programmer.
Errors are the most important phase of learning to code.

What are the common built-in data types in Python?

Python supports the below-mentioned built-in data types:

Immutable data types:

👉Number
👉String
👉Tuple

Mutable data types:

👉List
👉Dictionary
👉set

Python Most Important Interview Questions

Question 1: Calculate the average stock price for Company X over the last 6 months.

Question 2: Identify the month with the highest total sales for Company Y using their monthly sales data.

Question 3: Find the maximum and minimum stock price for Company Z on any given day in the last year.

Question 4: Create a column in the DataFrame showing the percentage change in stock price from the previous day for Company X.

Question 5: Determine the number of days when the stock price of Company Y was above its 30-day moving average. Question

6: Compare the average stock price of Companies X and Z in the first quarter of the year.

#Data#
----------------------------------------------
import pandas as pd
data = {   'Date': pd.date_range(start='2023-01-01', periods=180, freq='D'),   'CompanyX_StockPrice': pd.np.random.randint(50, 150, 180),   'CompanyY_Sales': pd.np.random.randint(20000, 50000, 180),   'CompanyZ_StockPrice': pd.np.random.randint(70, 200, 180) }

df = pd.DataFrame(data)

⌨️ Calculate derivatives in Python