# Today's learning--Pylint

## Concept of Pylint

Pylint is a popular <mark style="color:red;">**static code analysis tool**</mark> for Python programming language. It is designed to *check <mark style="color:orange;">Python code errors, style inconsistencies, and code smells</mark>.* Pylint <mark style="color:green;">analyzes the source code</mark> and <mark style="color:green;">provides feedback on various aspects</mark> such as *syntax errors, unused variables, undefined names, code complexity, and adherence to coding standards.*

The tool follows the guidelines outlined in the <mark style="color:red;">**Python Enhancement Proposal(PEP 8)**</mark> for coding style and help enfore best practices in Python development. Pylint assigns a numerical score to the code based on its analysis, allowing developers to assess the overall quality of their code.

Pylint performs its analysis by using <mark style="color:purple;">**combination of built-in and user-defined rules**</mark>. It generates reports that highlight potential issues and provides suggestions for improvement. The tool can <mark style="color:purple;">be integrated into various development environments</mark>, such as *text editors* and *development process*.

Pylint is highly configurable and allows developers to customize its behavior to suit their specific needs. It **supports a wide range of options** and can be extended with **plugin**s to incorporate additional rules or features.

Overall, Pylint is a valuable tool for Python developers to maintain code quality, improve consistency, and catch potential errors early in the development process.

## An example

```python
def factorial(n):
     if n==0:
         return 1
     else:
        return n* factorial(n-1)
num = 5
print(f"The factorial of {num} is {factorial(num)})
```

To run Pylint on this file, you can use the following commond in your terminal or command prompt:

```
pylint example.py

```

<mark style="color:purple;">After running this command, Pylint will analyze the code and provide a report with feedback. The report might include information about potential errors, style violations, and code smells. Here's simplified example of the Pylint report for the given code:</mark>

```python
**********Modle example
example.py:2:0: C0103: Function name "factorial" doesn't confirm to snake_case naming style (invalid-name)
examle.py:4:4: w0108: Redefining name 'num' from outer scope (redefined-outer-name)
example.py:6:16: C0304: Final newline missing (missing-fnal-newline)
-------------------------
Your code has been rated at 7.5/10
```

In this example, Pylint has flagged a few issues. It has identified that the function name "factorial" does not follow the snake\_case naming convention, suggested by the code's style guidlines. It has also indicated that the variable "num" is being redefined within the code, which might lead to confusion or unintended behavior. Lastly, it has notified that there is no final newline at the end of the file, which is recommended for better readability.

The rating at the end(7.5/10) represents an overall score for the code based on Pylint's analysis. The higher the score, the better the code adheres to the recommended guidelines and practoces.

By using the information provided in the Pylint report, developers can identify potential issues, refactor their code for improved style and clarity, and ensure better overall code quality.

## some specific meaning

* "py" indicates that the issue is found in a Python file.
* "2" refers to the line number in the file where the issue is located.
* "0" represents the column number, indicating the position within the line where the issue starts.

The line number and column number help pinpoint the exact location of the issue within the code, allowing developers to easily navigate and address the reported problems.

### what does C0103 means

In Pylint, the alphanumeric codes like "C0103" are identifiers for specific types of issues or messages. These codes provide a standardized way to categorize and reference the different types of warnings and errors reported by Pylint.

In the case of "C0103," it represents a convention-related warning or error. Here's the breakdown of the code:

* "C" indicates that it is a convention-related message.
* "0103" is a specific identifier for this type of convention issue.

In this case, the function name "factorial" does not conform to the <mark style="color:red;">**snake\_case naming style**</mark>, which is the convention of using lowercase letters and underscores between words in function names.

<mark style="color:green;">Snake\_case naming style is a convention for naming variables, functions, and other identifiers in programming languages. In snake\_case, words are written in lowercase letters, and multiple words are connected by underscores.</mark>

<mark style="color:green;">Here are a few examples of identifiers written in snake\_case:</mark>

* <mark style="color:green;">variable\_name</mark>
* <mark style="color:green;">function\_name</mark>
* <mark style="color:green;">module\_file\_name</mark>
* <mark style="color:green;">class\_name</mark>

### how to edit the code?

```python
def calculate_factorial(n):
        if n == 0: 
              return 1 
       else: 
              return n * calculate_factorial(n-1)
input_num = 5 
print(f"The factorial of {input_num} is {calculate_factorial(input_num)}")

#Add an empty line at the end
```

## Today's real code:

```python
name: Pylint

on: [push]

jobs:
  build:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        python-version: ["3.8", "3.9", "3.10"]
    steps:
    - uses: actions/checkout@v3
    - name: Set up Python ${{ matrix.python-version }}
      uses: actions/setup-python@v3
      with:
        python-version: ${{ matrix.python-version }}
    - name: Install dependencies
      run: |
        python -m pip install --upgrade pip
        pip install pylint
    - name: Analysing the code with pylint
      run: |
        pylint $(git ls-files '*.py')
```

\
The provided code appears to be a GitHub Actions workflow file written in YAML syntax. It defines a workflow named "Pylint" that runs when a push event occurs in the repository. Let's break down the different sections and steps of the workflow:

* **name**: Specifies the name of the workflow, which is "Pylint".
* **on**: Defines the trigger event that starts the workflow. In this case, the workflow runs when a push event occurs.
* **jobs**: Contains the definition of one or more jobs that should be executed as part of the workflow.
  * **build**: Defines a job named "build".
    * **runs-on**: Specifies the type of machine or environment on which the job runs. In this case, it runs on "ubuntu-latest".
    * **strategy**: Allows configuring a matrix of different job configurations. Here, it defines the "python-version" matrix with multiple Python versions.
    * **steps**: Contains a list of individual steps to be executed as part of the job.
      * **uses**: Fetches the latest repository code using the `actions/checkout` action.
      * **name**: Provides a name for the step, which is "Set up Python" followed by the Python version from the matrix.
      * **uses**: Installs the specified Python version using the `actions/setup-python` action.
      * **with**: Specifies the configuration for the `actions/setup-python` action, setting the Python version based on the matrix value.
      * **name**: Names the step "Install dependencies".
      * **run**: Runs the specified commands within the runner environment. In this case, it upgrades pip and installs the pylint package.
      * **name**: Names the step "Analysing the code with pylint".
      * **run**: Executes the `pylint` command on the Python files (`*.py`) in the repository using `git ls-files`.
