-\section{Standard module \sectcode{pdb}}
+\chapter{The Python Debugger}
\stmodindex{pdb}
\index{debugging}
-This module defines an interactive source code debugger for Python
-programs. It supports 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.
+\renewcommand{\indexsubitem}{(in module pdb)}
+
+The module \code{pdb} defines an interactive source code debugger for
+Python programs. It supports setting 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
\code{Pdb}. The extension interface uses the (also undocumented)
-modules \code{bdb} and \code{cmd}; it is currently undocumented.
+modules \code{bdb} and \code{cmd}; it is currently undocumented but
+easily understood by reading the source.
\ttindex{Pdb}
\ttindex{bdb}
\ttindex{cmd}
A primitive windowing version of the debugger also exists --- this is
-module \code{wdb}, which requires STDWIN.
+module \code{wdb}, which requires STDWIN (see the chapter on STDWIN
+specific modules).
\index{stdwin}
\ttindex{wdb}
in a slightly different way:
\begin{funcdesc}{run}{statement\optional{\, globals\optional{\, locals}}}
-Execute the \var{statement} (which should be a string) under debugger
+Execute the \var{statement} (given as a string) under debugger
control. The debugger prompt appears before any code is executed; you
-can set breakpoint and type \code{continue}, or you can step through
-the statement using \code{step} or \code{next}. 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.)
+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} (which should be a string) under
-debugger control. When \code{runeval()} returns, it returns the value
-of the expression. Otherwise this function is similar to
+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} (which should be a callable Python object, not
-a string) with the given arguments. When \code{runcall()} returns, it
-returns the return value of the function call. The debugger prompt
-appears as soon as the function is entered.
+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 code, even if the code is
-not otherwise being debugged.
+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}
\end{funcdesc}
\begin{funcdesc}{pm}{}
-Enter post-mortem debugging based on the traceback found in
+Enter post-mortem debugging of the traceback found in
\code{sys.last_traceback}.
\end{funcdesc}
With a \var{command} as argument, print help about that command.
``\code{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, ``\code{help exec}'' gives help on the ``\code{!}''
-command.
+through that command instead. Since the \var{command} argument must be
+an identifier, ``\code{help exec}'' must be entered to get help on the
+``\code{!}'' command.
\item[{w(here)}]
Move the current frame one level up in the stack trace
(to a newer frame).
-\item[{b(reak) [\var{lineno} \code{|} \var{function}]}]
+\item[{b(reak) [\var{lineno}\code{|}\var{function}]}]
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.
-\item[{cl(ear) [lineno]}]
+\item[{cl(ear) [\var{lineno}]}]
With a \var{lineno} argument, clear that break in the current file.
Without argument, clear all breaks (but first ask confirmation).
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 full speed, only stopping at
-the next line in the current function.)
+\code{next} executes called functions at (nearly) full speed, only
+stopping at the next line in the current function.)
\item[{r(eturn)}]
\item[{l(ist) [\var{first} [, \var{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 a count.
+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)}]
\item[{p \var{expression}}]
Evaluate the \var{expression} in the current context and print its
-value.
+value. (Note: \code{print} can also be used, but is not a debugger
+command --- this executes the Python \code{print} statement.)
\item[{[!] \var{statement}}]
-\section{Standard module \sectcode{pdb}}
+\chapter{The Python Debugger}
\stmodindex{pdb}
\index{debugging}
-This module defines an interactive source code debugger for Python
-programs. It supports 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.
+\renewcommand{\indexsubitem}{(in module pdb)}
+
+The module \code{pdb} defines an interactive source code debugger for
+Python programs. It supports setting 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
\code{Pdb}. The extension interface uses the (also undocumented)
-modules \code{bdb} and \code{cmd}; it is currently undocumented.
+modules \code{bdb} and \code{cmd}; it is currently undocumented but
+easily understood by reading the source.
\ttindex{Pdb}
\ttindex{bdb}
\ttindex{cmd}
A primitive windowing version of the debugger also exists --- this is
-module \code{wdb}, which requires STDWIN.
+module \code{wdb}, which requires STDWIN (see the chapter on STDWIN
+specific modules).
\index{stdwin}
\ttindex{wdb}
in a slightly different way:
\begin{funcdesc}{run}{statement\optional{\, globals\optional{\, locals}}}
-Execute the \var{statement} (which should be a string) under debugger
+Execute the \var{statement} (given as a string) under debugger
control. The debugger prompt appears before any code is executed; you
-can set breakpoint and type \code{continue}, or you can step through
-the statement using \code{step} or \code{next}. 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.)
+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} (which should be a string) under
-debugger control. When \code{runeval()} returns, it returns the value
-of the expression. Otherwise this function is similar to
+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} (which should be a callable Python object, not
-a string) with the given arguments. When \code{runcall()} returns, it
-returns the return value of the function call. The debugger prompt
-appears as soon as the function is entered.
+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 code, even if the code is
-not otherwise being debugged.
+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}
\end{funcdesc}
\begin{funcdesc}{pm}{}
-Enter post-mortem debugging based on the traceback found in
+Enter post-mortem debugging of the traceback found in
\code{sys.last_traceback}.
\end{funcdesc}
With a \var{command} as argument, print help about that command.
``\code{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, ``\code{help exec}'' gives help on the ``\code{!}''
-command.
+through that command instead. Since the \var{command} argument must be
+an identifier, ``\code{help exec}'' must be entered to get help on the
+``\code{!}'' command.
\item[{w(here)}]
Move the current frame one level up in the stack trace
(to a newer frame).
-\item[{b(reak) [\var{lineno} \code{|} \var{function}]}]
+\item[{b(reak) [\var{lineno}\code{|}\var{function}]}]
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.
-\item[{cl(ear) [lineno]}]
+\item[{cl(ear) [\var{lineno}]}]
With a \var{lineno} argument, clear that break in the current file.
Without argument, clear all breaks (but first ask confirmation).
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 full speed, only stopping at
-the next line in the current function.)
+\code{next} executes called functions at (nearly) full speed, only
+stopping at the next line in the current function.)
\item[{r(eturn)}]
\item[{l(ist) [\var{first} [, \var{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 a count.
+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)}]
\item[{p \var{expression}}]
Evaluate the \var{expression} in the current context and print its
-value.
+value. (Note: \code{print} can also be used, but is not a debugger
+command --- this executes the Python \code{print} statement.)
\item[{[!] \var{statement}}]
projects / thirdparty / Python / cpython.git / commitdiff
