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other:python:starting [2019/04/25 16:07]
jypeter Lots of changes 		other:python:starting [2019/05/17 08:56]
jypeter [Initialization] Improved
Line 29: Line 29:
 >>>​ >>>​
 </​code>​ </​code>​
 +
 +===== Ultra quick-start on the LSCE servers =====
 +
 +==== Initialization ====
 +
 +  - Start a terminal on an //obelix// server
 +  - Type ''​python''​ to access the //default Python 2// interpreter available on the servers...
 +  - ...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 //conda//
 +      * In a //bash// shell: ''​source ~jypeter/​.conda3_jyp.sh''​
 +      * 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 3.x: ''​conda activate cdatm_py3''​
 +    - Type ''​python''​ to start the interpreter
 +    - Note: if you will have to use python regularly, you should add the ''​source''​ line above to your ''​.cshrc''​ /''​.login''​ file (//tcsh// users) or ''​.bashrc''/''​.profile''​ (//bash// users)
 +      * **Do not** add the ''​conda activate cdatm_pyN''​ line to the shell config files, because this will create potential side-effects!\\ Only type this activation line in the terminals where you will need to use this specific version of Python
 +
 +==== 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 =====
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 Note: Anaconda provides and uses ''​conda''​ for its installation. Since UV-CDAT is now also installed and maintained with ''​conda'',​ you can read the [[other:​uvcdat:​conda_notes|Installing and maintaining UV-CDAT with conda]] page for more information,​ even if you are not going to use UV-CDAT Note: Anaconda provides and uses ''​conda''​ for its installation. Since UV-CDAT is now also installed and maintained with ''​conda'',​ you can read the [[other:​uvcdat:​conda_notes|Installing and maintaining UV-CDAT with conda]] page for more information,​ even if you are not going to use UV-CDAT
  
-===== Launching Python ​===== +===== ipython ​=====
- +
-Once you have initialized the [[#​some_python_distributions|python distribution]] you want to use, follow the instructions below to //start the interpreter from a shell// (on a Windows computer, you will have to start python from the //Start// menu or by clicking a shortcut on your desktop). +
- +
-Remember that on Linux/Mac you can check which python you are using by typing ''​which python''​! +
- +
-==== 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''​) ​ | +
- +
-==== Stand-alone script ==== +
- +
-A python script is just like any other shell 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''​).  +
- +
-<​code>​ +
-jypeter@asterix1 - ...jypeter - 54 >cat basic_script.py +
-#​!/​usr/​bin/​env python +
- +
-import sys +
- +
-script_name = sys.argv[0] +
- +
-print('​Hello world, I am the ' + script_name + ' script'​) +
- +
-# The end +
- +
-jypeter@asterix1 - ...jypeter - 55 >chmod +x basic_script.py +
- +
-ypeter@asterix1 - ...jypeter - 56 ># Type here what is required to initialize the distribution you want +
- +
-jypeter@asterix1 - ...jypeter - 57 >​./​basic_script.py +
-Hello world, I am the ./​basic_script.py script +
-</​code>​ +
- +
-==== Standard interpreter ==== +
- +
-  * ''​python'':​ start the interpreter +
-  * ''​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+
  
 ==== ipython interpreter ==== ==== ipython interpreter ====
other/python/starting.txt · Last modified: 2024/05/30 13:41 by jypeter

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