Using the PDB library debugger in Python _python

Python's own PDB library found it handy to debug a program with a PDB, and of course, what remote debugging, multithreading, and so on, the PDB is uncertain.

There are several options to use PDB debugging:

1. Command line to start the target program, plus the-m parameter, so call myscript.py Word breakpoint is the execution of the program before the first line

Copy Code code as follows:

PYTHON-M PDB myscript.py

2. Enable debugging in a python interactive environment

Copy Code code as follows:

>>> Import PDB
>>> Import MyModule
>>> Pdb.run (' mymodule.test () ')

3. More commonly used is to insert a program in the middle of the program, as opposed to a breakpoint in the General IDE and then start debug, but this way is hardcode

Copy Code code as follows:

if __name__ = = "__main__":
A = 1
Import PDB
Pdb.set_trace ()
b = 2
c = A + b
Print (c)

Then run the script normally, and by the Pdb.set_trace (), you'll see the debugger's prompt (PDB).

Common Debugging commands

H (ELP), print the current version of the PDB available commands, if you want to query a command, you can enter H [command], such as: "H L"-View List command
L (IST), which lists the code blocks that are currently going to be run

Copy Code code as follows:

(PDB) L
497 Pdb.set_trace ()
498 Base_data = {}
499 new_data = {}
Try:
501 execfile (base_file_name,{},base_data)
502-> execfile (new_file_name,{},new_data)
503 except:
504 Logger.writelog ("error! Load result log error! ")
505 print "Load CMP logs error!"
506 Raise Exception, "load CMP logs error!"
40V

B (reak), set breakpoints, such as "B 77″, is the current script in the 77 lines of the breakpoint, can also enter the function name as a parameter, the breakpoint hit the specific function entry, if only B, will show all existing breakpoints

Copy Code code as follows:

(PDB) B 504
Breakpoint 4 at/home/jchen/regression/regressionlogcmp.py:504

Condition Bpnumber [Condition], set a conditional breakpoint, the following statement is the 4th breakpoint plus the condition "a==3"
(Pdb) Condition 4 a==3
(PDB) b
Num Type Disp Enb Where
4 Breakpoint Keep Yes at/home/jchen/regression/regressionlogcmp.py:504
Stop only if a==3

CL (ear) that, if followed by an argument, clears the specified breakpoint (I've never succeeded in Python2.4!!! If you remove all breakpoints without parameters

Copy Code code as follows:

(PDB) CL
Clear all breaks? Y

Disable/enable, disabling/activating breakpoints

Copy Code code as follows:

(Pdb) Disable 3
(PDB) b
Num Type Disp Enb Where
3 Breakpoint Keep No at/home/jchen/regression/regressionlogcmp.py:505

N (EXT), let the program run the next line, if the current statement has a function call, with n is not going into the body of the called function

S (TEP), similar to n, but if there is currently a function call, then S will go into the called function body
C (ont (inue)) to allow the program to run normally until a breakpoint is encountered
J (UMP), let the program jump to the specified number of lines

Copy Code code as follows:

(PDB) J 497
>/home/jchen/regression/regressionlogcmp.py (497) Comparelog ()
-> Pdb.set_trace ()

A (RGS), print the parameters of the current function

Copy Code code as follows:

(PDB) A
_logger =
_base =./base/mrm-8137.log
_new =./new/mrm-8137.log
_caseid = 5550001
_tostepnum = 10
_cmpmap = {' _bcmpbinarylog ': ' true ', ' _bcmplog ': ' true ', ' _bcmpresp ': ' True '}

P, one of the most useful commands to print a variable

Copy Code code as follows:

(PDB) P _new
U './new/mrm-8137.log '

！ , the exclamation point followed by the statement, you can directly change a variable
Q (uit), exit debug
It is also interesting to find that debugging a program at the command line, record it and share it.

W, Print a stack trace, with the most recent frame at the bottom. An arrow indicates the ' Current frame ', which determines the context of most commands. ' BT ' is a alias for this command.

D, move the "current" frame one level down in the stack trace
(to a newer frame).

U, move the "current" frame one level up in the stack trace
(to a older frame).

Using the U and D commands, we can switch between stack frames to get information about their related context variables. W can display some of the most recent stack frame information.