# Learn Python

*Python is an interpreted, object-oriented, high-level programming language with dynamic semantics, known for its readability and ease of use.*

---

## What is Python?
Python is a high-level, general-purpose programming language known for its simplicity and readability. It's widely used in fields ranging from web development and data analysis, to scientific computing, automation, and HPC workflows.

### Python Basics
#### Variables

Variables in Python are dynamic, meaning you don't have to declare their data type.
```python
name = "Chloe"
age = 30
pi = 3.14159
```

#### Data Types

Despite not needing to declare the data type of a variable, Python still associates every value with a data type. These data types determine how Python treats and processes data.

|**Type**|**Description**        |**Example**        |
|:------:|:----------------------|:-----------------:|
| `int`  |Integer numbers        | `42`              |
|`float` |Decimal numbers        | `3.14`            |
|`str`   |String of characters   | `"hello"`         |
|`bool`  |Boolean logic          | `True`            |
| `list` |Ordered, changeable    | `[1. 2, 3,]`      |
|`tuple` |Ordered, unchangeable  | `(1, 2)`          |
| `dict` |Key-value pairs        |`{"name": "Chloe"}`|
| `set`  |Unordered unique values| `{1, 2, cat, dog}`|

#### Conditional Statements

Conditional statements are control mechanisms that allow a program to execute different blocks of code based on whether a specific condition is met.
```python
if x > 0:
    print("positive")
elif x < 0:
    print("negative")
else:
    print("zero")
```

**If**

The `if` statement is the most basic type of conditional statement. It executes a block of code only if the associating condition is true.
```python
if condition:
    # code to execute if the condition is true
```
**If-Else**

The `if-else` statement provides an alternate path of execution if the associated condition is false. 
```python
if condition:
    # code to execute if condition is true
else
    # code to execute if the condition is false
```

**If-Elif-Else**

The `if-elif-else` statement allows for the checking of multiple conditions. If the `if` condition is false, the `elif` conditions are checked in order, and if neither the `if` or the `elif` conditions are true, the `else` block is exexecuted.
```python
if condition1:
    # code to execute if condition1 is true
elif condition2:
    # code to execute if condition1 is fasle, and condition2 is true
else:
    # code to execute if all preceding conditions are false
```

#### Loops

A loop is a control flow mechanism that allows code to be executed repeatedly, continuing repetition for a specified number of times or until a condition is met.

**For**

The `for` loop is used for iterating over a sequence of objects. The loop executes the code block once for each item in the sequence.

```python
colors = ["red", "blue", "yellow"]
for color in colors:
    print(color)
```

**While**

The `while` loop is used to execute a code block repeatedly as long as the given condition remains true. The loop continues until the condition is false.

```python
count = 0
while count < 5:
    print(count)
    count += 1
```

#### Functions

Functions let you reuse blocks of code and structure logic clearly.
```python
def greet(name):
    return f"Hello, {name}!"
```

Some functions come built into Python and are commonly used like, `print()` or `len()`. A complete list of built-in Python functions can be found [here](https://docs.python.org/3/library/functions.html)

### Working with Libraries
Python libraries are a collection of pre-written, reusable code modules that extend Python's functionality and allow programmers to perform various tasks without having to write code from scratch.
- [**The Python Standard Library**](https://docs.python.org/3/library/index.html) is a collection of modules and packages that are included with the Python installation.
- [**The Python Package Index (PyPI)**](https://pypi.org/) is an additional active collection of hundreds of thousands of components, from individual programs and modules to packages and entire application development frameworks. PyPI acts as a central hub where developers can share and find Python packages and libraries. PyPI integrates with the `pip` package manager, making it simple to install packages directly from the index.

Use `import` to add built-in or external libraries to your code base:
```python
import math
print(math.sqrt(16))
```

Some common libraries include:
- `numpy` - numerical computing
- `scipy` - scientific tools
- `matplotlib` - plotting
- `pandas` - dataframes

---
## Resources
- [Offical Docs](https://docs.python.org/3/): Python's offical documentation site.
- [Python for Beginners](https://www.python.org/about/gettingstarted/): A helpful resource for installing and learning Python.
- [Python for Non-Programmers](https://wiki.python.org/moin/BeginnersGuide/NonProgrammers): A list of resources for those new to programming and Python.
- [Beginners Guide to Python](https://wiki.python.org/moin/BeginnersGuide/Programmers): A list of resources for those with some programming experience.
- [Google's Python Class](https://developers.google.com/edu/python): A free Python tutorial with videos and code exercises.
- [Learn Python](https://www.learnpython.org/): An interactive in-the-browser tutorial for learning Python.
- [PyPI](https://pypi.org/): A repository of software for the Python programming language.
- [The Python Standard Library](https://docs.python.org/3/library/index.html): Deep dive into Python's standard library.
- [Built-in Functions](https://docs.python.org/3/library/functions.html): A list of functions built-in to the python interpreter.