other:python:starting
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other:python:starting [2019/04/26 07:35] jypeter Added Ultra quick-start on the LSCE servers |
other:python:starting [2019/04/26 09:57] jypeter Improved the quick start section |
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| - Start a terminal on an //obelix// server | - Start a terminal on an //obelix// server | ||
| - | - Type ''python'' to access the //default Python 2// interpreter or follow the steps below for a more advanced distribution. Remember that **you can exit the interpreter by typing CTRL-D** (or ''quit()'' or ''exit()'') | + | - Type ''python'' to access the //default Python 2// interpreter or follow the steps below to use the more complete //CDAT// distribution. Remember that **you can exit the interpreter by typing CTRL-D** (or ''quit()'' or ''exit()'') |
| - | - Determine if you are using a [[other:newppl:starting#which_shell_are_you_using|bash or tcsh shell]], then type the following command to initialize python | + | - Determine if you are using a [[other:newppl:starting#which_shell_are_you_using|bash or tcsh shell]], then type the following command to initialize //conda// |
| - | - In a //bash// shell: ''source ~jypeter/.conda3_jyp.sh'' | + | * In a //bash// shell: ''source ~jypeter/.conda3_jyp.sh'' |
| - | - In a //tcsh// shell: ''source ~jypeter/.conda3_jyp.csh'' | + | * In a //tcsh// shell: ''source ~jypeter/.conda3_jyp.csh'' |
| + | - Choose which //flavor// of Python you want by typing: | ||
| + | * Python 2.7.x: ''conda activate cdatm_py2'' | ||
| + | * Python 2.7.x: ''conda activate cdatm_py3'' | ||
| + | - Type ''python'' to start the interpreter | ||
| + | |||
| + | ==== Useful keyboard shortcuts ==== | ||
| + | |||
| + | ^ Key ^ Effect ^ | ||
| + | | **CTRL-D** | Exit the interpreter | | ||
| + | | **↑ and ↓** | Go to previous/next line(s) | | ||
| + | | **CTRL-A** | Go to the beginning of the line | | ||
| + | | **CTRL-E** | Go to the end of the line | | ||
| + | | **CTRL-K** | Erase from the cursor to the end of the line | | ||
| + | | **CTRL-U** | Erase from the beginning of the line to the cursor | | ||
| + | | **TAB** x 2 | Do some TAB-completion (context dependent)\\ e.g. ''a = np.cum**TABTAB**'' | | ||
| + | | **CTRL-C** | Interrupt a running script | | ||
| + | | **CTRL-Z** | Suspend the interpreter and go back to the shell\\ **Do not forget** to go back to the interpreter with ''fg''\\ or to kill it (with ''jobs'' and ''kill %NN'') | | ||
| + | |||
| + | ==== Executing a python script ==== | ||
| + | |||
| + | Note: Python is an [[https://en.wikipedia.org/wiki/Interpreted_language|interpreted language]] and we speak of //Python scripts// rather than //Python programs//. | ||
| + | |||
| + | * ''python'': start the interpreter and start working interactively | ||
| + | * ''python script.py'': execute //script.py// and **exit** | ||
| + | * ''python -i script'': execute //script.py// and **stay in the interpreter** (''-i'' = //**I**nteractive//) | ||
| + | |||
| + | Type ''man python'' if you want to see what other command line options are available | ||
| + | |||
| + | ==== Stand-alone script ==== | ||
| + | |||
| + | You don't have to explicitly call the python interpreter, if the interpreter is specified in a ''#!'' [[https://en.wikipedia.org/wiki/Shebang_%28Unix%29|shebang comment]] on **the first line of the script** with, and the script has its //execution bit// set (''chmod +x my_script.py''). | ||
| + | |||
| + | If you have a ''basic_script.py'' file with the following content in a directory... | ||
| + | <code> | ||
| + | #!/usr/bin/env python | ||
| + | |||
| + | import sys | ||
| + | |||
| + | script_name = sys.argv[0] | ||
| + | |||
| + | print('Hello world, I am the ' + script_name + ' script') | ||
| + | |||
| + | # The end</code> | ||
| + | |||
| + | ...and if you are in the same directory and have initialized the Python distribution you want, you can then run the script the following way: | ||
| + | |||
| + | <code> > chmod +x basic_script.py | ||
| + | |||
| + | > ls -l basic_script.py | ||
| + | -rwxr-xr-x [...] basic_script.py | ||
| + | |||
| + | > ./basic_script.py | ||
| + | Hello world, I am the ./basic_script.py script | ||
| + | </code> | ||
| + | |||
| + | ==== What next? ==== | ||
| + | |||
| + | - Read the rest of this page to get a better understanding of what you have learned in this section, and use Python more efficiently | ||
| + | - Learn Python by reading what you need on the [[other:python:jyp_steps|JYP's recommended steps for learning python]] page | ||
| ===== Python distributions available for LSCE users ===== | ===== Python distributions available for LSCE users ===== | ||
other/python/starting.txt · Last modified: 2024/05/30 13:41 by jypeter
