other:python:jyp_steps
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other:python:jyp_steps [2016/02/09 15:32] jypeter Added the views side effect section |
other:python:jyp_steps [2016/05/20 13:41] jypeter Added a link to 'Working with Python' at the top |
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| ====== JYP's recommended steps for learning python ====== | ====== JYP's recommended steps for learning python ====== | ||
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| + | <note tip>If you don't know which python distribution to use and how to start the python interpreter, you should first read the [[starting|Working with Python]] page</note> | ||
| As can be expected, there is **a lot** of online python documentation available, and it's easy to get lost. You can always use google to find an answer to your problem, and you will probably end up looking at lots of answers on [[http://stackoverflow.com/questions/tagged/python|Stack Overflow]] or a similar site. But it's always better to know where you can find some good documentation... and to spend some time to read the documentation | As can be expected, there is **a lot** of online python documentation available, and it's easy to get lost. You can always use google to find an answer to your problem, and you will probably end up looking at lots of answers on [[http://stackoverflow.com/questions/tagged/python|Stack Overflow]] or a similar site. But it's always better to know where you can find some good documentation... and to spend some time to read the documentation | ||
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| * [[http://blog.codinghorror.com/a-pragmatic-quick-reference/|A Pragmatic Quick Reference]] | * [[http://blog.codinghorror.com/a-pragmatic-quick-reference/|A Pragmatic Quick Reference]] | ||
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| + | ===== Debugging your code ===== | ||
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| + | There is only so much you can do with staring at your code in your favorite text editor, and adding ''print'' lines in your code (or using [[https://docs.python.org/2/howto/logging.html#logging-basic-tutorial|logging]] instead of ''print''). The next step is to **use the python debugger**! | ||
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| + | ==== Debugging in text mode ==== | ||
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| + | - Start the script with: ''python -m pdb my_script.py'' | ||
| + | - Type ''run'' (or **r**) to go to the first line of the script | ||
| + | - Type ''continue'' (or **c**) to execute the script to the end, or till the first breakpoint or error is reached | ||
| + | - Use ''where'' (or **w**) to check the call stack that led to the current stop. Use ''up'' and ''down'' to navigate through the call stack and examine the values of the functions' parameters | ||
| + | - Type ''break NNN'' to stop at line NNN | ||
| + | - Use ''type(var)'' and ''print var'' to check the type and values of variables. You can also change the variables' values on the fly! | ||
| + | - Type ''run'' (or **r**) to restart the script | ||
| + | - Use ''next'' and ''step'' to execute some parts of the script line by line. If a code line calls a function: | ||
| + | * ''next'' (or **n**) will execute a function and stop on the next line | ||
| + | * ''step'' (or **s**) will stop at the first line **inside the function** | ||
| + | - Check the [[https://docs.python.org/2/library/pdb.html#debugger-commands|debugger commands]] for details, or type ''help'' in the debugger for using the built-in help | ||
| + | |||
| + | ==== Using pydebug ==== | ||
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| + | Depending on the distribution, the editor and the programming environment you use, you may have access to a graphical version of the debugger. UV-CDAT users can use ''pydebug my_script.py'' | ||
| ===== Improving the performance of your code ===== | ===== Improving the performance of your code ===== | ||
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| Hint: before optimizing your script, you should spent some time //profiling// it, in order to only spend time improving the slow parts of your script | Hint: before optimizing your script, you should spent some time //profiling// it, in order to only spend time improving the slow parts of your script | ||
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| + | ==== Useful packages ==== | ||
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| + | * [[https://github.com/pydata/numexpr|Numexpr]]: //Numexpr is a **fast numerical expression evaluator for NumPy**. With it, expressions that operate on arrays (like "3*a+4*b") are accelerated and use less memory than doing the same calculation in Python.// | ||
| + | * [[http://www.pytables.org/|PyTables]]: //PyTables is a package for managing hierarchical datasets and designed to efficiently and **easily cope with extremely large amounts of data**// | ||
| ==== Tutorials by Ian Osvald ==== | ==== Tutorials by Ian Osvald ==== | ||
other/python/jyp_steps.txt · Last modified: 2024/03/07 10:15 by jypeter
