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diff --git a/Doc/libpdb.tex b/Doc/libpdb.tex deleted file mode 100644 index 50a841e..0000000 --- a/Doc/libpdb.tex +++ /dev/null @@ -1,298 +0,0 @@ -\chapter{The Python Debugger} -\label{module-pdb} -\stmodindex{pdb} -\index{debugging} - - -The module \code{pdb} defines an interactive source code debugger for -Python programs. It supports setting -(conditional) breakpoints and single stepping -at the source line level, inspection of stack frames, source code -listing, and evaluation of arbitrary Python code in the context of any -stack frame. It also supports post-mortem debugging and can be called -under program control. - -The debugger is extensible --- it is actually defined as a class -\class{Pdb}. -\withsubitem{(class in pdb)}{\ttindex{Pdb}} -This is currently undocumented but easily understood by reading the -source. The extension interface uses the (also undocumented) modules -\module{bdb}\refstmodindex{bdb} and \module{cmd}\refstmodindex{cmd}. - -A primitive windowing version of the debugger also exists --- this is -module \module{wdb}, which requires \module{stdwin} (see the chapter -on STDWIN specific modules). -\refbimodindex{stdwin} -\refstmodindex{wdb} - -The debugger's prompt is \samp{(Pdb) }. -Typical usage to run a program under control of the debugger is: - -\begin{verbatim} ->>> import pdb ->>> import mymodule ->>> pdb.run('mymodule.test()') -> <string>(0)?() -(Pdb) continue -> <string>(1)?() -(Pdb) continue -NameError: 'spam' -> <string>(1)?() -(Pdb) -\end{verbatim} - -\file{pdb.py} can also be invoked as -a script to debug other scripts. For example: - -\begin{verbatim} -python /usr/local/lib/python1.5/pdb.py myscript.py -\end{verbatim} - -Typical usage to inspect a crashed program is: - -\begin{verbatim} ->>> import pdb ->>> import mymodule ->>> mymodule.test() -Traceback (innermost last): - File "<stdin>", line 1, in ? - File "./mymodule.py", line 4, in test - test2() - File "./mymodule.py", line 3, in test2 - print spam -NameError: spam ->>> pdb.pm() -> ./mymodule.py(3)test2() --> print spam -(Pdb) -\end{verbatim} - -The module defines the following functions; each enters the debugger -in a slightly different way: - -\begin{funcdesc}{run}{statement\optional{, globals\optional{, locals}}} -Execute the \var{statement} (given as a string) under debugger -control. The debugger prompt appears before any code is executed; you -can set breakpoints and type \code{continue}, or you can step through -the statement using \code{step} or \code{next} (all these commands are -explained below). The optional \var{globals} and \var{locals} -arguments specify the environment in which the code is executed; by -default the dictionary of the module \code{__main__} is used. (See -the explanation of the \code{exec} statement or the \code{eval()} -built-in function.) -\end{funcdesc} - -\begin{funcdesc}{runeval}{expression\optional{, globals\optional{, locals}}} -Evaluate the \var{expression} (given as a a string) under debugger -control. When \code{runeval()} returns, it returns the value of the -expression. Otherwise this function is similar to -\code{run()}. -\end{funcdesc} - -\begin{funcdesc}{runcall}{function\optional{, argument, ...}} -Call the \var{function} (a function or method object, not a string) -with the given arguments. When \code{runcall()} returns, it returns -whatever the function call returned. The debugger prompt appears as -soon as the function is entered. -\end{funcdesc} - -\begin{funcdesc}{set_trace}{} -Enter the debugger at the calling stack frame. This is useful to -hard-code a breakpoint at a given point in a program, even if the code -is not otherwise being debugged (e.g. when an assertion fails). -\end{funcdesc} - -\begin{funcdesc}{post_mortem}{traceback} -Enter post-mortem debugging of the given \var{traceback} object. -\end{funcdesc} - -\begin{funcdesc}{pm}{} -Enter post-mortem debugging of the traceback found in -\code{sys.last_traceback}. -\end{funcdesc} - -\section{Debugger Commands} - -The debugger recognizes the following commands. Most commands can be -abbreviated to one or two letters; e.g. ``\code{h(elp)}'' means that -either ``\code{h}'' or ``\code{help}'' can be used to enter the help -command (but not ``\code{he}'' or ``\code{hel}'', nor ``\code{H}'' or -``\code{Help} or ``\code{HELP}''). Arguments to commands must be -separated by whitespace (spaces or tabs). Optional arguments are -enclosed in square brackets (``\code{[]}'') in the command syntax; the -square brackets must not be typed. Alternatives in the command syntax -are separated by a vertical bar (``\code{|}''). - -Entering a blank line repeats the last command entered. Exception: if -the last command was a ``\code{list}'' command, the next 11 lines are -listed. - -Commands that the debugger doesn't recognize are assumed to be Python -statements and are executed in the context of the program being -debugged. Python statements can also be prefixed with an exclamation -point (``\code{!}''). This is a powerful way to inspect the program -being debugged; it is even possible to change a variable or call a -function. When an -exception occurs in such a statement, the exception name is printed -but the debugger's state is not changed. - -\begin{description} - -\item[h(elp) \optional{\var{command}}] - -Without argument, print the list of available commands. With a -\var{command} as argument, print help about that command. \samp{help -pdb} displays the full documentation file; if the environment variable -\code{PAGER} is defined, the file is piped through that command -instead. Since the \var{command} argument must be an identifier, -\samp{help exec} must be entered to get help on the \samp{!} command. - -\item[w(here)] - -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. - -\item[d(own)] - -Move the current frame one level down in the stack trace -(to an older frame). - -\item[u(p)] - -Move the current frame one level up in the stack trace -(to a newer frame). - -\item[b(reak) \optional{\var{lineno}\code{\Large|}\var{function}% - \optional{, \code{'}\var{condition}\code{'}}}] - -With a \var{lineno} argument, set a break there in the current -file. With a \var{function} argument, set a break at the entry of -that function. Without argument, list all breaks. -If a second argument is present, it is a string (included in string -quotes!) specifying an expression which must evaluate to true before -the breakpoint is honored. - -\item[cl(ear) \optional{\var{lineno}}] - -With a \var{lineno} argument, clear that break in the current file. -Without argument, clear all breaks (but first ask confirmation). - -\item[s(tep)] - -Execute the current line, stop at the first possible occasion -(either in a function that is called or on the next line in the -current function). - -\item[n(ext)] - -Continue execution until the next line in the current function -is reached or it returns. (The difference between \code{next} and -\code{step} is that \code{step} stops inside a called function, while -\code{next} executes called functions at (nearly) full speed, only -stopping at the next line in the current function.) - -\item[r(eturn)] - -Continue execution until the current function returns. - -\item[c(ont(inue))] - -Continue execution, only stop when a breakpoint is encountered. - -\item[l(ist) \optional{\var{first\optional{, last}}}] - -List source code for the current file. Without arguments, list 11 -lines around the current line or continue the previous listing. With -one argument, list 11 lines around at that line. With two arguments, -list the given range; if the second argument is less than the first, -it is interpreted as a count. - -\item[a(rgs)] - -Print the argument list of the current function. - -\item[p \var{expression}] - -Evaluate the \var{expression} in the current context and print its -value. (Note: \code{print} can also be used, but is not a debugger -command --- this executes the Python \code{print} statement.) - -\item[\optional{!}\var{statement}] - -Execute the (one-line) \var{statement} in the context of -the current stack frame. -The exclamation point can be omitted unless the first word -of the statement resembles a debugger command. -To set a global variable, you can prefix the assignment -command with a ``\code{global}'' command on the same line, e.g.: - -\begin{verbatim} -(Pdb) global list_options; list_options = ['-l'] -(Pdb) -\end{verbatim} - -\item[q(uit)] - -Quit from the debugger. -The program being executed is aborted. - -\end{description} - -\section{How It Works} - -Some changes were made to the interpreter: - -\begin{itemize} -\item \code{sys.settrace(\var{func})} sets the global trace function -\item there can also a local trace function (see later) -\end{itemize} - -Trace functions have three arguments: \var{frame}, \var{event}, and -\var{arg}. \var{frame} is the current stack frame. \var{event} is a -string: \code{'call'}, \code{'line'}, \code{'return'} or -\code{'exception'}. \var{arg} depends on the event type. - -The global trace function is invoked (with \var{event} set to -\code{'call'}) whenever a new local scope is entered; it should return -a reference to the local trace function to be used that scope, or -\code{None} if the scope shouldn't be traced. - -The local trace function should return a reference to itself (or to -another function for further tracing in that scope), or \code{None} to -turn off tracing in that scope. - -Instance methods are accepted (and very useful!) as trace functions. - -The events have the following meaning: - -\begin{description} - -\item[\code{'call'}] -A function is called (or some other code block entered). The global -trace function is called; arg is the argument list to the function; -the return value specifies the local trace function. - -\item[\code{'line'}] -The interpreter is about to execute a new line of code (sometimes -multiple line events on one line exist). The local trace function is -called; arg in None; the return value specifies the new local trace -function. - -\item[\code{'return'}] -A function (or other code block) is about to return. The local trace -function is called; arg is the value that will be returned. The trace -function's return value is ignored. - -\item[\code{'exception'}] -An exception has occurred. The local trace function is called; arg is -a triple (exception, value, traceback); the return value specifies the -new local trace function - -\end{description} - -Note that as an exception is propagated down the chain of callers, an -\code{'exception'} event is generated at each level. - -For more information on code and frame objects, refer to the -\emph{Python Reference Manual}. |