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Untabified and applied Richard Wolff's changes (plus my own reflowing 

of some paragraphs).
This commit is contained in:
Guido van Rossum 1998-09-17 15:01:38 +00:00
parent 3a98e78a6e
commit fc076d4ce2
1 changed files with 106 additions and 156 deletions
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Lib/pdb.doc
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@ -3,8 +3,8 @@ The Python Debugger Pdb
To use the debugger in its simplest form: To use the debugger in its simplest form:
>>> import pdb >>> import pdb
>>> pdb.run('<a statement>') >>> pdb.run('<a statement>')
The debugger's prompt is '(Pdb) '. This will stop in the first The debugger's prompt is '(Pdb) '. This will stop in the first
function call in <a statement>. function call in <a statement>.
@ -13,10 +13,10 @@ Alternatively, if a statement terminated with an unhandled exception,
you can use pdb's post-mortem facility to inspect the contents of the you can use pdb's post-mortem facility to inspect the contents of the
traceback: traceback:
>>> <a statement> >>> <a statement>
<exception traceback> <exception traceback>
>>> import pdb >>> import pdb
>>> pdb.pm() >>> pdb.pm()
The commands recognized by the debugger are listed in the next The commands recognized by the debugger are listed in the next
section. Most can be abbreviated as indicated; e.g., h(elp) means section. Most can be abbreviated as indicated; e.g., h(elp) means
@ -35,208 +35,158 @@ debugged; it is even possible to change variables. When an exception
occurs in such a statement, the exception name is printed but the occurs in such a statement, the exception name is printed but the
debugger's state is not changed. debugger's state is not changed.
The debugger supports aliases, which can save typing. And aliases The debugger supports aliases, which can save typing. And aliases can
can have parameters (see the alias help entry) which allows one a have parameters (see the alias help entry) which allows one a certain
certain level of adaptability to the context under examination. level of adaptability to the context under examination.
Multiple commands may be entered on a single line, separated by Multiple commands may be entered on a single line, separated by the
semi-colons. No intelligence is applied to separating the commands; pair ';;'. No intelligence is applied to separating the commands; the
the input is split at the first ';', even if it is in the middle of input is split at the first ';;', even if it is in the middle of a
a quoted string. quoted string.
If a file ".pdbrc" exists in your home directory or in the current If a file ".pdbrc" exists in your home directory or in the current
directory, it is read in and executed as if it had been typed at directory, it is read in and executed as if it had been typed at the
the debugger prompt. This is particularly useful for aliases. debugger prompt. This is particularly useful for aliases. If both
If both files exist, the one in the home directory is read first files exist, the one in the home directory is read first and aliases
and aliases defined there can be overriden by the local file. defined there can be overriden by the local file.
Aside from aliases, the debugger is not directly programmable; but Aside from aliases, the debugger is not directly programmable; but it
it is implemented as a class from which you can derive your own is implemented as a class from which you can derive your own debugger
debugger class, which you can make as fancy as you like. class, which you can make as fancy as you like.
Debugger commands Debugger commands
================= =================
h(elp) h(elp)
Without argument, print the list of available commands. Without argument, print the list of available commands. With
With a command name as argument, print help about that command a command name as argument, print help about that command
(this is currently not implemented). (this is currently not implemented).
w(here) w(here)
Print a stack trace, with the most recent frame at the bottom. Print a stack trace, with the most recent frame at the bottom.
An arrow indicates the "current frame", which determines the An arrow indicates the "current frame", which determines the
context of most commands. context of most commands.
d(own) d(own)
Move the current frame one level down in the stack trace Move the current frame one level down in the stack trace
(to an older frame). (to an older frame).
u(p) u(p)
Move the current frame one level up in the stack trace Move the current frame one level up in the stack trace
(to a newer frame). (to a newer frame).
b(reak) [ ([filename:]lineno | function) [, "condition"] ] b(reak) [ ([filename:]lineno | function) [, condition] ]
With a filename:line number argument, set a break there. If With a filename:line number argument, set a break there. If
filename is omitted, use the current file. With a function name, filename is omitted, use the current file. With a function
set a break at the first executable line of that function. name, set a break at the first executable line of that
Without argument, list all breaks. Each breakpoint is assigned function. Without argument, list all breaks. Each breakpoint
a number which is by all the other breakpoint commands refer to it. is assigned a number to which all the other breakpoint
commands refer.
The condition argument, if present, is a string which must The condition argument, if present, is a string which must
evaluate to true in order for the breakpoint to be honored. evaluate to true in order for the breakpoint to be honored.
tbreak [ ([filename:]lineno | function) [, "condition"] ] tbreak [ ([filename:]lineno | function) [, condition] ]
Temporary breakpoint, which is removed automatically when it is Temporary breakpoint, which is removed automatically when it
first hit. The arguments are the same as break. is first hit. The arguments are the same as break.
cl(ear) [bpnumber [bpnumber ...] ] cl(ear) [bpnumber [bpnumber ...] ]
With a space separated list of breakpoint numbers, clear those With a space separated list of breakpoint numbers, clear those
breakpoints. Without argument, clear all breaks (but first breakpoints. Without argument, clear all breaks (but first
ask confirmation). ask confirmation).
disable bpnumber [bpnumber ...] disable bpnumber [bpnumber ...]
Disables the breakpoints given as a space separated list of Disables the breakpoints given as a space separated list of
breakpoint numbers. Disabling a breakpoint means it cannot cause breakpoint numbers. Disabling a breakpoint means it cannot
the program to stop execution, but unlike clearing a breakpoint, it cause the program to stop execution, but unlike clearing a
remains in the list of breakpoints and can be (re-)enabled. breakpoint, it remains in the list of breakpoints and can be
(re-)enabled.
enable bpnumber [bpnumber ...] enable bpnumber [bpnumber ...]
Enables the breakpoints specified. Enables the breakpoints specified.
ignore bpnumber count ignore bpnumber count
Sets the ignore count for the given breakpoint number. If Sets the ignore count for the given breakpoint number. If
count is omitted, the ignore count is set to 0. A breakpoint count is omitted, the ignore count is set to 0. A breakpoint
becomes active when the ignore count is zero. When non-zero, becomes active when the ignore count is zero. When non-zero,
the count is decremented each time the breakpoint is reached the count is decremented each time the breakpoint is reached
and the breakpoint is not disabled and any associated condition and the breakpoint is not disabled and any associated
evaluates to true. condition evaluates to true.
condition bpnumber str_condition condition bpnumber condition
str_condition is a string specifying an expression which condition is an expression which must evaluate to true before
must evaluate to true before the breakpoint is honored. the breakpoint is honored. If condition is absent, any
If str_condition is absent, any existing condition is removed; existing condition is removed; i.e., the breakpoint is made
i.e., the breakpoint is made unconditional. unconditional.
s(tep) s(tep)
Execute the current line, stop at the first possible occasion Execute the current line, stop at the first possible occasion
(either in a function that is called or in the current function). (either in a function that is called or in the current function).
n(ext) n(ext)
Continue execution until the next line in the current function Continue execution until the next line in the current function
is reached or it returns. is reached or it returns.
r(eturn) r(eturn)
Continue execution until the current function returns. Continue execution until the current function returns.
c(ont(inue)) c(ont(inue))
Continue execution, only stop when a breakpoint is encountered. Continue execution, only stop when a breakpoint is encountered.
l(ist) [first [,last]] l(ist) [first [,last]]
List source code for the current file. List source code for the current file.
Without arguments, list 11 lines around the current line Without arguments, list 11 lines around the current line
or continue the previous listing. or continue the previous listing.
With one argument, list 11 lines starting at that line. With one argument, list 11 lines starting at that line.
With two arguments, list the given range; With two arguments, list the given range;
if the second argument is less than the first, it is a count. if the second argument is less than the first, it is a count.
a(rgs) a(rgs)
Print the argument list of the current function. Print the argument list of the current function.
p expression p expression
Print the value of the expression. Print the value of the expression.
(!) statement (!) statement
Execute the (one-line) statement in the context of the current Execute the (one-line) statement in the context of the current
stack frame. The exclamation point can be omitted unless the stack frame. The exclamation point can be omitted unless the
first word of the statement resembles a debugger command. first word of the statement resembles a debugger command. To
To assign to a global variable you must always prefix the assign to a global variable you must always prefix the command
command with a 'global' command, e.g.: with a 'global' command, e.g.:
(Pdb) global list_options; list_options = ['-l'] (Pdb) global list_options; list_options = ['-l']
(Pdb) (Pdb)
whatis arg whatis arg
Prints the type of the argument. Prints the type of the argument.
alias [name [command]] alias [name [command]]
Creates an alias called 'name' that executes 'command'. The command Creates an alias called 'name' that executes 'command'. The
must *not* be enclosed in quotes. Replaceable parameters can be command must *not* be enclosed in quotes. Replaceable
indicated by %1, %2, and so on, while %* is replaced by all the parameters can be indicated by %1, %2, and so on, while %* is
parameters. If no command is given, the current alias for name replaced by all the parameters. If no command is given, the
is shown. If no name is given, all aliases are listed. current alias for name is shown. If no name is given, all
aliases are listed.
Aliases may be nested and can contain anything that can be Aliases may be nested and can contain anything that can be
legally typed at the pdb prompt. Note! You *can* override legally typed at the pdb prompt. Note! You *can* override
internal pdb commands with aliases! Those internal commands internal pdb commands with aliases! Those internal commands
are then hidden until the alias is removed. Aliasing is recursively are then hidden until the alias is removed. Aliasing is
applied to the first word of the command line; all other words recursively applied to the first word of the command line; all
in the line are left alone. other words in the line are left alone.
As an example, here are two useful aliases (especially when placed As an example, here are two useful aliases (especially when
in the .pdbrc file): placed in the .pdbrc file):
#Print instance variables (usage "pi classInst") #Print instance variables (usage "pi classInst")
alias pi for k in %1.__dict__.keys(): print "%1." + k + "=" + %1.__dict__[k] alias pi for k in %1.__dict__.keys(): print "%1.",k,"=",%1.__dict__[k]
#Print instance variables in self #Print instance variables in self
alias ps pi self alias ps pi self
unalias name unalias name
Deletes the specified alias. Deletes the specified alias.
q(uit) q(uit)
Quit from the debugger. Quit from the debugger.
The program being executed is aborted. The program being executed is aborted.
How it works
============
Some changes were made to the interpreter:
- sys.settrace(func) sets the global trace function
- there can also a local trace function (see later)
Trace functions have three arguments: (frame, event, arg)
- frame is the current stack frame
- event is a string: 'call', 'line', 'return' or 'exception'
- arg is dependent on the event type
A trace function should return a new trace function or None.
Class methods are accepted (and most useful!) as trace methods.
The events have the following meaning:
'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.
'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.
'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.
'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
Note that as an exception is propagated down the chain of callers, an
'exception' event is generated at each level.
Stack frame objects have the following read-only attributes:
f_code: the code object being executed
f_lineno: the current line number (-1 for 'call' events)
f_back: the stack frame of the caller, or None
f_locals: dictionary containing local name bindings
f_globals: dictionary containing global name bindings
Code objects have the following read-only attributes:
co_code: the code string
co_names: the list of names used by the code
co_consts: the list of (literal) constants used by the code
co_filename: the filename from which the code was compiled