:::section{.main}
## Online Python Compiler

To start your programming journey you first need to understand what compilers are. Compilers are the computer software that converts your high-level source code to executable machine-level instructions made up of 0s and 1s, that can be understood by the computer.

Compilers scan the high-level code line by line and show different kinds of errors present in the code on the command line.

Scaler Topics comes with an IDE that is very feasible enough to compile, test, and run **Python programs online** easily for free.
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:::section{.main}
## Working of the Python 3 Compiler (IDE)

Given below are some of the steps of our Compiler that users might find helpful:

The first step is your need to sign in to use this compiler's features. It is possible to run your code without signing in but you will not have a track to your previous codes here, so it's advisable to sign in to enjoy its cool features. Click on the button present at the top right corner and a window will appear.

- **Code Editor**: Write code in the code editor (which has syntax highlighting for more code readability). For users who are logged into the Scaler Topics Platform, the total number of characters in their code can go up to five thousand characters. For non Scaler Topics Users, their Python code can have up to five hundred characters.
- **RUN**: In order to run a Python program, a user can write python code in the editor and then click on the ‘RUN’ button after selecting the appropriate compiler version.
- **SAVE**: The Python code written in the editor can be saved by clicking on the ‘SAVE’ button on the top right corner of the webpage. The saved codes can be accessed using the ‘MY SNIPPETS ’ button of the webpage.
-** STDIN & STDOUT**: In order to feed input to the Python Code, users can use the Standard Input (stdin) console of our compiler and the output of the code appears on the Standard Output (stdout) of the compiler.
- **SAVE**: The programs saved can be made public - available for all - or private - accessible to only the code owner.
- **FORK**: Public code snippets can also be forked or downloaded in the ‘NEW’ section using the ‘FORK’ button. After forking a code, one can reuse it as per requirement.
- **SHARE**: Now that you have your code ready, you might need to share it with people. Our compiler also supports sharing of code in Read-Only Format. This can be done using the ‘SHARE’ button on the top right corner of the webpage.

Example:
```python
if __name__ == "__main__":
   num = 10
   
   if num > 0:
      print(num, "is a positive number.")
   else:
      print(num, "is a negative number.")
```

Output:
```plaintext
10 is a positive number.
```
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## Learn Python- Practice Online

### What is Python?

**Python** is an object-oriented, interpreted, high-level programming language that allows programmers to write commands that can be understood by computers. It has a comprehensive standard library. Python is now one of the most popular and widely used programming languages due to its very simple syntax and dynamic nature.

### Why Learn Python?

Python is one of the highly used programming languages in various technologies like web development, machine learning, data science, etc. It has the following features:
This language is freely available and open-sourced i.e. its source code is available in public.

- It is easy to learn as it has simple code syntax that can be easily understood. One can learn it in just a few hours.
- It is an Object-Oriented programming language, i.e. it supports concepts of classes, objects, encapsulation, data abstraction, inheritance, etc.
- It is a platform-independent programming language i.e if you wish to run a python code written in windows to some other platform like Linux, then you have no need to change it.
- It has a lot of built-in libraries that help programmers in making development fast and efficient which saves time.
- Python can be interpreted line by line unlike other languages like C++, Java, etc. So it becomes easy for a programmer to find and resolve the errors that arise while coding.
- You do not need to manage the memory in Python.
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## Python Syntax

Python has various syntax rules that are scanned by IDEs. Following are some of the basic syntax that one should know to start their programming career in Python:

### Loops (for loop, while loop, do-while loop)

Loops are used when there is the need to repeatedly execute a block of statements, for example printing the numbers from 1 to 5. Let’s execute this using all the three loops in our Scaler Topics IDE.

**for loop**

Syntax:
```python
for val in sequence:
    # statement(s)
```

Example:
```python=
for i in range(0, 6):
    print(i)
```

Output:
```plaintext
0
1
2
3
4
5
```

**while loop**

Syntax:
```python
while expression:
   statement(s)
```

Example:
```python
c = 0
while (c < 3):   
    c = c + 1
    print("Hello")
```

Output:
```plaintext
Hello
Hello
Hello
```

### Conditional statements (if/else)

Python supports various decision-making statements like if, if..else, nested if, switch case. We have discussed the basic one:

**If..else**

Syntax:
```python
if(conditional_expression):
    # code
else:
    # code
```

Example:
```python
num = 10
if num > 0:
   print(num, "is a positive number.")
else:
   print(num, "is a negative number.")
```

Output:
```plaintext
10 is a positive number.
```

### Functions

Functions in python are the block of statements performing a specific task. It divides our large python program into smaller modules that are easy to manage and are organized. There is no repetition of similar statements and increases code reusability.

Syntax:

```python
def function_name(parameters):
    # code statement(s)
```

Example:

```python
def wishes(name):
   print("Hello, " + name + ". Good morning!")

wishes("John") # function call
```
Output:

```plaintext
Hello, John. Good morning!
```
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## How to write a program in Python?

We have gone through various examples for Python programs, and they were easily understandable. In this section, we will discuss some lines of codes in python for your understanding. 

```python
print("Hello World")
print(1 + 2)
print("1" + "2")
```

Output:
```plaintext
Hello World
3
12
```

- **Line 1**: The first line simply prints the “Hello World” message by passing it as an argument in the print statement.

- **Line 2**: This line prints the addition result of two numbers by passing an operator and operands as an argument in the print statement.

- **Line 3**: The third line prints the concatenation of two strings which is done using a plus sign by passing two strings as an argument in the print statement.
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## How to compile and run the Python programs online?

Following are the steps to [compile and run](https://www.scaler.com/topics/how-to-run-python-program/) a python program:

- The first step is to install python on your system
- Set the path variable
- You can check your python by typing `python` on cmd.
- Write your python program
- Save it with a name, let's say `hello.py` (python files are saved with `.py` extension)
- Open cmd.exe
- Go to the path where you saved your `hello.py` file,
- Type `python hello.py` and press enter key.
Results are displayed on cmd.

And in the case of online compilers, you just need to type your code and click on the Compile/Run button. You can see your results in the output window.
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## Additional Resources

- [Python for Beginners Course](https://www.scaler.com/topics/course/python-for-beginners/)
- [Python Tutorial](https://www.scaler.com/topics/python/)
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:::section{.main}
## Glossary
    
- **Online IDE**: IDE is an acronym for Integrated Development Environment. Online   Integrated Development Environments help programmers code in various languages and run, compile and debug their codes online without having the need to download the respective programming compilers.
- **Compiler**: In computing, a compiler is a computer program that is used to translate computer codes written in one programming language into another language.
- **Interpreter**: Like Compilers, interpreters are also used to translate computer codes written in one programming language into another language. However, the difference between the two is that compilers compile the entire source code into machine code at once while interpreters convert the source code into machine code line by line.
- **Code Editor**: A code editor is software used by programmers to code. Most code editors provide various features like syntax highlighting to make the code written on them more readable.
- **Coding Ground**: Coding grounds are platforms that can be used to write and run codes written in various languages.
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