debugger.txt
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Debugger

 Debugging *activity* is much more than using the debugger *tool*.
  Texbook has lots of good advice about debugging, nothing about debugger tool.

 Python debugger tool pdb is, in effect, an enhancement of the interpreter
  You should be familiar with using the interpreter to investigate behavior
  BUT interpreter only works at top level - can't access local variables in fcns
  Debugger is an interpreter that works in any local environment,
   can use debugger *inside* a function call, read/set local variables  

 Debugger tool can be an alternative to adding lots of print statements

 pdb occasionally useful but I usually resort to print statements

 Assertions are also useful: assert <boolean expression>, raise exception if false










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Debugger method/commands

 Demo:  
  $ python -i repetition.py
  >>> import pdb
  >>> pdb.run('fact_recurse(3)')
  > ... status ...
  (Pdb) 

 At (Pdb) prompt:

  b foo.py:99  - set breakpoint in file:line
  c - continue to next breakpoint
  w - where, print stack, names and locations in all pending function calls
  p x - print value of variable or expression x (disambiguate from Pdb commands)
  s - step, execute next statement, steps into functions
  n - next, excecute next statement, execute entire function call

  ... or any other Python statement, if different from Pdb command ...