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 [2016/02/23 10:03] jypeter Added links to Numexpr and PyTables |
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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]] | ||
| + | |||
| + | ===== Debugging your code ===== | ||
| + | |||
| + | 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**! | ||
| + | |||
| + | ==== Debugging in text mode ==== | ||
| + | |||
| + | - 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 ==== | ||
| + | |||
| + | 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 | ||
| + | |||
| + | ==== Useful packages ==== | ||
| + | |||
| + | * [[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
