How to Write a Basic Python Program

Python is a high-level programming language. The language utilizes a straightforward syntax which can make it easy for new users to get started. ==== Install the Dependencies ====

Part 1 of 2:

Environment Set Up

Install the Dependencies

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Open the Terminal. On Linux, you can press the Alt button to open a search bar. Type "terminal" and click on Terminal.
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Know the commands. Terminal commands are shown in this document as:
1. ```
command -options filename.ext 
```
2. ```
sudo apt-get install build-essential 
```
  1. The "sudo" command gives permission to the terminal to modify your computer. This is necessary to install any program. You will be required to enter your password.
3. The "apt-get install" command tells the computer to install the package "build-essential" which is required to install Python.
4. ```
sudo apt-get install libreadline-gplv2-dev libncursesw5-dev libssl-dev libsqlite3-dev tk-dev libgdbm-dev libc6-dev libbz2-dev 
```
5. These are programs that Python uses to run correctly. They are also known as 'dependencies'.

Download and Extract Python

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Download the latest version of Python from the Internet. Use the following command:
1. ```
cd ~/Downloads/ 
```
2. The "cd" command changes to the correct working directory so the computer can find and put programs in the right place.
3. ```
wget http://python.org/ftp/python/2.7.5/Python-2.7.5.tgz 
```
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Decompress the Python file using the following command:
1. ```
tar -xvf Python-2.7.5.tgz 
```
2. ```
cd Python-2.7.5 
```
3. Once again, we need to change the working directory. This time, we change to the newly created Python directory.

Install Python

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Use the ./configure command checks your computer to ensure you have all the necessary components to install Python. It will alert you of any critical errors.
1. ```
./configure 
```
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Use the make command. It compiles the source code and creates the executables.
1. ```
make 
```
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Move the applications and libraries. With the following command, all of the applications and libraries associated with Python are moved into the correct places on your computer.
1. ```
sudo make install 
```

Part 2 of 2:

Use Python

Write the Script

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Open a text editor.
1. Any text editor that can save files with a ".py" extension will do. Ubuntu 12.04 or greater is packaged with the Gedit editor.
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Type
```
print 'Hello, World!' 
```
1. In Python, whatever is enclosed in quotes after the word print will be printed out to the screen.
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Save the file as "hello_world.py.
1. Be careful that the file is not saved as "hello_world.py.txt".

Run the Script

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Open the Terminal again.
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Navigate to the directory where "hello_world.py" is located.
1. Remember to use the "cd" command to change directories.
2. If you need a list of all subdirectories at your current location, use the "ls" command. "ls" stands for "list subdirectories".
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Run the script:
1. ```
python hello_world.py 
```

python command install -dev

Lesley Montoya

Update 05 March 2020

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