Debugging


Code profiling is an attempt to find bottlenecks in your code. Profiling is supposed to find what parts of your code take the longest. Once you know that, then you can look at those pieces of your code and try to find ways to optimize it. Python comes with three profilers built in: cProfile, profile and hotshot. According to the Python documentation, hotshot “no longer maintained and may be dropped in a future version of Python”. The profile module is a pure Python module, but adds a lot of overhead to profiled programs. Thus we will be focusing on cProfile, which has an interface that mimics the profile module. (more…)

PyChecker is a cool tool for checking Python scripts for bugs. It works with Python 2.0 – 2.7. In this article, we will write some crappy code to see what PyChecker can pick up on. Then we’ll improve the code according to what we find until the code checks out. According to PyChecker’s website, it can detect the following problems:

  • No global found (e.g., using a module without importing it)
  • Passing the wrong number of parameters to functions/methods/constructors
  • Passing the wrong number of parameters to builtin functions & methods
  • Using format strings that don’t match arguments
  • Using class methods and attributes that don’t exist
  • Changing signature when overriding a method
  • Redefining a function/class/method in the same scope
  • Using a variable before setting it
  • self is not the first parameter defined for a method
  • Unused globals and locals (module or variable)
  • Unused function/method arguments (can ignore self)
  • No doc strings in modules, classes, functions, and methods

(more…)