---
title: Tutorial 02
---

## Creating an User-Defined Python Package

1. Create a top level folder (e.g.: `ws` ) with the following sub-directory structure

        tutorials
            t02
                calculator
                    calculator_package



---


2. Open a console/terminal within the `calculator` directory, activate the conda enviroment and start VS Code from the command line:
```
conda activate pta
code .
```


---



3. Using VS Code create the following files under their respective directories

    ./`calculate.py`

    ./calculator_package/`__init__.py`

    ./calculator_package/`calculator.py`


---



4. In the `calculator.py` create a `Calculator` Python class:
```python
class Calculator:

    def get_version():
        return "1.0.0"

    def sum(self, val1, val2):
        """ Sum of 2 values """
        pass

    def sub(self, val1, val2):
        """ Subtract of 2 values """
        pass

    def mul(self, val1, val2):
        """ Multiply of 2 values """
        pass

    def div(self, val1, val2):
        """ Divide of 2 values """
        pass

    def exp(self, val1):
        """ Return e raised to the power x """
        pass

    def sqr(self, val1):
        """ Square root of a number """
        pass

    def ln(self, val1):
        """ Natural log of a number """
        pass
```


---


5. Content of `__init__.py`:
```python
__version__ = "1.0.0"
```


---


6. Content of `calculate.py`:
```python
from calculator_package.calculator import Calculator

if __name__ == '__main__':
    try:
        calculator = Calculator()
        print(calculator.get_version())  ## it will fail, find out why
    except Exception as e:
        print(e)
```


---


7. In VS Code have as active open file `calculate.py` and from the `Run` menu select `Start Debugging` to run the Python code.


---


8. Fix any issues and implement the Calculator functionality


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9. Run `calculate.py` form the command line:
```
python calculate.py
```

10. Run `calculator.py` form the command line within the `calculator` directory:
```
python calculator_package/calculator.py
```


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