Added Chapter 4 of Level 1 of Python Tutorial

docs/python-tutorial/chapters/04-built-in-functions-pt-1.md

@@ -0,0 +1,113 @@
+---
+description: Built-in Functions Part 1
+---
+
+# Built-in Functions Part 1
+
+!!! note
+
+    This chapter will only cover how to use some built-in functions. So, for now, consider functions as
+    helper code which does some specific task and is pre-written for you to use. You will learn about
+    functions in great detail later in this tutorial, so don't worry about that for now.
+
+Python has many built-in functions which you can use to make your life easier. In this section, we
+will take a look at `print`, `input` and some type-casting functions in detail.
+
+## `print()`
+
+The `print` function is used to print/show something on the screen (also known as the terminal or
+standard output). With this, you can write the first program that every programmer writes when they
+learn a new language:
+
+```python
+print("Hello World!") # Output: Hello World!
+```
+
+This line of code will print `Hello World!` on your screen. You can also print any other data type
+(such as `int`, `float`, or `bool`) using `print`.
+
+```python
+print("My name is Alex") # Output: My name is Alex
+print(56) # Output: 56
+print(3.14) # Output: 3.14
+print(False) # Output: False
+```
+
+You can also print the data currently present in a variable using `print`.
+
+```python
+a = 5
+print(a) # Output: 5
+a = "python"
+print(a) # Output: python
+```
+
+Each `print` statement prints on a new line. You can print multiple things using a single `print`
+statement by separating them using commas (`,`), which will result in all the values being printed
+on the same line separated by spaces.
+
+```python
+print("Value of pi is", 3.14) # Output: Value of pi is 3.14
+```
+
+!!! note
+
+    Keep in mind that this works only in `print` and CANNOT be used to combine different strings or
+    variables with strings otherwise.
+
+## `input()`
+
+The `input` function is used to take input from the user through the terminal (also known as the
+standard input). It returns everything the user types until the user hits the `Enter`/ `Return` key
+on the keyboard. You can also give a `str` to the `input` function which will be displayed on the
+screen while taking the input. For example:
+
+```python
+input("Enter your name: ")
+```
+
+The above code will print `Enter your name: ` followed by a blinking cursor where you can type the
+actual input. Now, to actually use the value the user entered, you need to assign the value returned
+by the `input` function to a variable.
+
+```python
+name = input("Enter your name: ")
+print(name)
+```
+
+The `input` function returns the input as a `str`, so the variable `name` will be of type `str`. The
+output of above code will be whatever the user entered.
+
+## Type Casting
+
+Now you know how to take input from the user, but, the `input` function returns a `str` no matter
+what the user types. So, for example, if the user types `54`, it will return a `str` (`"54"`), not
+an `int` (`54`). So, if you want to use the number the user entered, you will need to convert the
+`str` returned by `input` to an `int`. This process of converting one data type to another is called
+**type casting**.
+
+There are two types of type casting:
+
+1. **Implicit Type Casting**: It is done automatically by Python when it is needed.
+2. **Explicit Type Casting**: It is done manually by the programmer.
+
+### Explicit Type Casting
+
+Python has many built-in functions for explicit type casting, and they are named the same as the
+data type they cast to. Here is the list of type-casting functions with the type they cast to:
+
+| Function  | Type |
+|-----------|------|
+| `bool()`  | `bool` |
+| `float()` | `float` |
+| `int()`   | `int` |
+| `str()`   | `str` |
+
+For example, you can do this to get a number from the user:
+
+```python
+number_string = input("Enter a number: ")
+number_int = int(number_string)
+```
+
+Similarly, you can use other functions according to the data type you need.

docs/python-tutorial/chapters/index.md

@@ -12,7 +12,7 @@ in-depth Python features.
 - [Brief Python History](01-python-history.md)
 - [Introduction to Variables](02-intro-to-variables.md)
 - [Data Types pt 1 (`string`, `int`, `float` & `bool`)](03-data-types-pt01.md)
-- Builtin Functions pt 1 (`print` & `input` and type casting)
+- [Builtin Functions pt 1 (`print` & `input` and type casting)](04-built-in-functions-pt-1.md)
 - String Interpolation & Concatenation (f-strings, str.format & +)
 - Operators pt 1 (Comparison & Arithmetic)
 - Conditional Statements (`if`, `else` & `elif`)

zensical.toml

@@ -24,6 +24,7 @@ nav = [
       "python-tutorial/chapters/01-python-history.md",
       "python-tutorial/chapters/02-intro-to-variables.md",
       "python-tutorial/chapters/03-data-types-pt01.md",
+      "python-tutorial/chapters/04-built-in-functions-pt-1.md",
   ] },
   { "Resources" = [
     "resources/index.md",