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    "# Introduction to Python \n",
    "\n",
    "-- _for Economists and Statisticians_\n",
    "\n",
    "Feng Li\n",
    "\n",
    "School of Statistics and Mathematics\n",
    "\n",
    "Central University of Finance and Economics\n",
    "\n",
    "[feng.li@cufe.edu.cn](mailto:feng.li@cufe.edu.cn)\n",
    "\n",
    "[https://feng.li/python](https://feng.li/python)"
   ]
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   "source": [
    "## Ecomists' _old_ toolbox\n",
    "\n",
    "\n",
    "### Data\n",
    "\n",
    "- GDP, GNP, usually with fewer observations\n"
   ]
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    "### Software\n",
    "\n",
    "\n",
    "- Economists have relied on **Stata** for over 30 years because of its breadth, accuracy, extensibility, and reproducibility. \n",
    "\n",
    "- Whether you are researching school selection, minimum wage, GDP, or stock trends, Stata provides all the statistics, graphics, and data-management tools needed to pursue a broad range of economic questions."
   ]
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   "source": [
    "## Why Python?\n",
    "\n",
    "- Python is a widely used general-purpose, high-level programming language. \n",
    "\n",
    "- Its design philosophy emphasizes code readability, and its syntax allows programmers to express concepts in fewer lines of code than would be possible in languages such as C++ or Java. \n",
    "\n",
    "- The language provides constructs intended to enable clear programs on both a small and large scale."
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   "source": [
    "## Python Features\n",
    "\n",
    "The core philosophy of the language is summarized by the document \"PEP 20 (The Zen of Python)\" as\n",
    "- Beautiful is better than ugly\n",
    "- Explicit is better than implicit\n",
    "- Simple is better than complex\n",
    "- Complex is better than complicated\n",
    "- Readability counts\n",
    "\n"
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    "\n",
    "**Python is compact and readable**. Programs written in Python are typically much shorter than equivalent C, C++, or Java programs.\n",
    "\n",
    "**Python is extensible**: if you know how to program in C, it is easy to add a new built-in function or module to the interpreter, either to perform critical operations at maximum speed."
   ]
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   "source": [
    "## Why we should use Python?\n",
    "\n",
    "- Open source!\n",
    "\n",
    "- Easy to learn and use with no programing experiences.\n",
    "\n",
    "- Rich ecosystem for modeling and data analysis"
   ]
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   "source": [
    "## Fun fact!\n",
    "\n",
    "The language is named after the BBC show `Monty Python’s Flying Circus` (1969-1974) and has nothing to do with reptiles."
   ]
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   "source": [
    "## Python modules\n",
    "\n",
    "- Python has a large standard library, commonly cited as one of Python's greatest strengths, providing tools suited to many tasks. \n",
    "\n",
    "- The standard library is **not essential** to run Python or embed Python within an application. \n",
    "\n",
    "- As of March 2018, the Python package Index (PyPI), the official repository for third-party Python software, contains over 130,000 packages with a wide range of functionality.\n",
    "\n",
    "- Notable applications: web scraping, scientific computing, text processing, image processing"
   ]
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   "source": [
    "## Installing Python\n",
    "\n",
    "\n",
    "- Python is free software.\n",
    "\n",
    "- On Windows and Mac, Anaconda (https://www.anaconda.com/) is the easiest way to perform Python data science and machine learning on a single machine.\n",
    "\n",
    "- To install Python on other systems, check out the [Python Setup and Usage section in Python help documentation](https://docs.python.org/3.9/using/index.html)."
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   "source": [
    "## Using Python 3\n",
    "\n",
    "\n",
    "- To start a Python interpreter, type the command in your terminal: `python3`.\n",
    "\n",
    "- To terminate the Python interpreter, type an end-of-file character (`Control-D` on Unix, `Control-Z` on Windows) at the primary prompt. If that doesn’t work, you can exit the interpreter by typing the following command: `quit()`.\n",
    "\n",
    "```sh\n",
    "fli@carbon:~$ python3\n",
    "Python 3.9.7 (default, Sep 24 2021, 09:43:00) \n",
    "[GCC 10.3.0] on linux\n",
    "Type \"help\", \"copyright\", \"credits\" or \"license\" for more information.\n",
    ">>>\n",
    "```"
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    "## Executing Python scripts\n",
    "\n",
    "- Write down your Python script and name it as `hello.py` with `.py` extension\n",
    "    ```sh\n",
    "    #!/usr/bin/env python3\n",
    "    print('Hello World')\n",
    "    ```\n",
    "- Go to your terminal, and run it with Python interpreter \n",
    "    ```sh\n",
    "    python3 hello.py\n",
    "    ```    \n",
    "- You could also make your script _executable_ (like .exe file on Windows)\n",
    "    ```sh\n",
    "    chmod +x hello.py\n",
    "    ```\n",
    "- Run the script in your terminal\n",
    "    ```sh\n",
    "    ./hello.py\n",
    "    ```"
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   "source": [
    "## Using interactive Python shell\n",
    "\n",
    "IPython is a command shell for interactive computing in multiple programming languages\n",
    "\n",
    "- Interactive shells (terminal and Qt-based).\n",
    "- Jupyter notebook with support for code, text, mathematical expressions, inline plots and other media.\n",
    "- Support for interactive data visualization and use of GUI toolkits.\n",
    "- Flexible, embeddable interpreters to load into one's own projects.\n",
    "- Tools for parallel computing.\n",
    "\n",
    "To start IPython interactive environment, type `ipython` in your terminal."
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   "source": [
    "## Getting Python help\n",
    "\n",
    "- Help for Python module `help('module')`\n",
    "- Help for Python function `help(function)`. \n",
    "- Use `q` to quit the help session.\n",
    "\n",
    "- With IPython, use the command `?function` or `function?`. `??function` or `function??` can also be used to type the entire function including both the `docstring` and the code.\n",
    "\n",
    "- This is the official documentation is available at https://docs.python.org/3.9/"
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   "source": [
    "## Text Editors/IDEs\n",
    "\n",
    "To edit Python code, you just need a handy text editor. There are many available, check out the following pages \n",
    "\n",
    "- Spider: Anaconda's build-in editor\n",
    "- Visual Studio Code (https://code.visualstudio.com/Download)\n",
    "- Sublime Text (https://www.sublimetext.com/download)\n"
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    "## Coding Style\n",
    "\n",
    "\n",
    "\n",
    "- Use 4-space indentation, and no tabs.\n",
    "\n",
    "- Wrap lines so that they don't exceed 79 characters.\n",
    "\n",
    "- Use blank lines to separate functions and classes, and larger blocks of code inside functions.\n",
    "\n",
    "- When possible, put comments on a line of their own."
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    "- Use `docstrings`.\n",
    "\n",
    "- Use spaces around operators and after commas, but not directly inside bracketing constructs: `a = f(1, 2) + g(x=3, y=4)`.\n",
    "\n",
    "- use **CamelCase** for classes and **lower_case_with_underscores** for functions and methods. \n",
    "\n",
    "- Always use `self` as the name for the first method argument.\n",
    "\n",
    "- Do not use fancy encodings even if Python 3 has full UTF support. Plain ASCII works best in any case."
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