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GNU Info File
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1996-11-14
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52KB
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1,017 lines
This is Info file pylibi, produced by Makeinfo-1.55 from the input file
lib.texi.
This file describes the built-in types, exceptions and functions and the
standard modules that come with the Python system. It assumes basic
knowledge about the Python language. For an informal introduction to
the language, see the Python Tutorial. The Python Reference Manual
gives a more formal definition of the language. (These manuals are not
yet available in INFO or Texinfo format.)
Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam, The
Netherlands.
All Rights Reserved
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the names of Stichting Mathematisch
Centrum or CWI or Corporation for National Research Initiatives or CNRI
not be used in advertising or publicity pertaining to distribution of
the software without specific, written prior permission.
While CWI is the initial source for this software, a modified version
is made available by the Corporation for National Research Initiatives
(CNRI) at the Internet address ftp://ftp.python.org.
STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH
CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
THIS SOFTWARE.
File: pylibi, Node: Debugger Commands, Next: How It Works, Prev: The Python Debugger, Up: The Python Debugger
Debugger Commands
=================
The debugger recognizes the following commands. Most commands can be
abbreviated to one or two letters; e.g. "`h(elp)'" means that either
"`h'" or "`help'" can be used to enter the help command (but not "`he'"
or "`hel'", nor "`H'" or "`Help' or "`HELP'"). Arguments to commands
must be separated by whitespace (spaces or tabs). Optional arguments
are enclosed in square brackets ("`[]'") in the command syntax; the
square brackets must not be typed. Alternatives in the command syntax
are separated by a vertical bar ("`|'").
Entering a blank line repeats the last command entered. Exception: if
the last command was a "`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 ("`!'"). 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.
h(elp) [COMMAND
]
Without argument, print the list of available commands. With a
COMMAND as argument, print help about that command. "`help pdb'"
displays the full documentation file; if the environment variable
`PAGER' is defined, the file is piped through that command
instead. Since the COMMAND argument must be an identifier, "`help
exec'" must be entered to get help on the "`!'" command.
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.
d(own)
Move the current frame one level down in the stack trace (to an
older frame).
Move the current frame one level up in the stack trace (to a newer
frame).
b(reak) [LINENO`|'FUNCTION
]
With a LINENO argument, set a break there in the current file.
With a FUNCTION argument, set a break at the entry of that
function. Without argument, list all breaks.
cl(ear) [LINENO
]
With a LINENO argument, clear that break in the current file.
Without argument, clear all breaks (but first ask confirmation).
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).
n(ext)
Continue execution until the next line in the current function is
reached or it returns. (The difference between `next' and `step'
is that `step' stops inside a called function, while `next'
executes called functions at (nearly) full speed, only stopping at
the next line in the current function.)
r(eturn)
Continue execution until the current function returns.
c(ont(inue))
Continue execution, only stop when a breakpoint is encountered.
l(ist) [FIRST [, 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.
a(rgs)
Print the argument list of the current function.
p EXPRESSION
Evaluate the EXPRESSION in the current context and print its
value. (Note: `print' can also be used, but is not a debugger
command -- this executes the Python `print' statement.)
STATEMENT]
Execute the (one-line) 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
"`global'" command on the same line, e.g.:
(Pdb) global list_options; list_options = ['-l']
(Pdb)
q(uit)
Quit from the debugger. The program being executed is aborted.
File: pylibi, Node: How It Works, Prev: Debugger Commands, Up: The Python Debugger
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''
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 fro