pdb
— Python 调试器
¶
源代码： Lib/pdb.py
模块
pdb
为 Python 程序定义交互源代码调试器。它支持在源代码行级别设置 (条件) 断点和单步执行、审查堆栈帧、列出源代码、及在任何堆栈帧上下文中评估任意 Python 代码。它支持事后调试，且还可以在程序控制下被调用。
调试器可扩展 – 实际上，它被定义成类
Pdb
。这目前未文档化，但通过阅读源代码很容易理解。扩展接口使用模块
bdb
and
cmd
.
调试器提示为
(Pdb)
。在调试器控制下运行程序的典型用法：
>>> import pdb >>> import mymodule >>> pdb.run('mymodule.test()') > <string>(0)?() (Pdb) continue > <string>(1)?() (Pdb) continue NameError: 'spam' > <string>(1)?() (Pdb)
3.3 版改变：
Tab 补全凭借
readline
模块可用于命令和命令自变量，如：提供当前全局和局部名称作为自变量为
p
命令。
pdb.py
还可以援引作为调试其它脚本的脚本。例如：
python3 -m pdb myscript.py
When invoked as a script, pdb will automatically enter post-mortem debugging if the program being debugged exits abnormally. After post-mortem debugging (or after normal exit of the program), pdb will restart the program. Automatic restarting preserves pdb’s state (such as breakpoints) and in most cases is more useful than quitting the debugger upon program’s exit.
3.2 版新增：
pdb.py
现在接受
-c
选项执行命令，就像给定在
.pdbrc
文件，见
调试器命令
.
The typical usage to break into the debugger from a running program is to insert
import pdb; pdb.set_trace()
at the location you want to break into the debugger. You can then step through the code following this statement, and continue running without the debugger using the
continue
命令。
审查崩溃程序的典型用法：
>>> import pdb >>> import mymodule >>> mymodule.test() Traceback (most recent call last): File "<stdin>", line 1, in <module> 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)
The module defines the following functions; each enters the debugger in a slightly different way:
pdb.
run
(
语句
,
globals=None
,
locals=None
)
¶
执行
语句
(given as a string or a code object) under debugger control. The debugger prompt appears before any code is executed; you can set breakpoints and type
continue
, or you can step through the statement using
step
or
next
(all these commands are explained below). The optional
globals
and
locals
arguments specify the environment in which the code is executed; by default the dictionary of the module
__main__
is used. (See the explanation of the built-in
exec()
or
eval()
functions.)
pdb.
runeval
(
表达式
,
globals=None
,
locals=None
)
¶
评估
表达式
(given as a string or a code object) under debugger control. When
runeval()
returns, it returns the value of the expression. Otherwise this function is similar to
run()
.
pdb.
runcall
(
function
,
*args
,
**kwds
)
¶
调用
function
(a function or method object, not a string) with the given arguments. When
runcall()
returns, it returns whatever the function call returned. The debugger prompt appears as soon as the function is entered.
pdb.
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).
pdb.
post_mortem
(
traceback=None
)
¶
Enter post-mortem debugging of the given traceback 对象。若无 traceback is given, it uses the one of the exception that is currently being handled (an exception must be being handled if the default is to be used).
pdb.
pm
(
)
¶
Enter post-mortem debugging of the traceback found in
sys.last_traceback
.
The
run*
函数和
set_trace()
是别名对于实例化的
Pdb
类且调用同名方法。若想要访问进一步特征，自己必须这样做：
pdb.
Pdb
(
completekey='tab'
,
stdin=None
,
stdout=None
,
skip=None
,
nosigint=False
)
¶
Pdb
是调试器类。
The
completekey
,
stdin
and
stdout
自变量会被传递给底层
cmd.Cmd
类；见这里的描述。
The skip argument, if given, must be an iterable of glob-style module name patterns. The debugger will not step into frames that originate in a module that matches one of these patterns. [1]
By default, Pdb sets a handler for the SIGINT signal (which is sent when the user presses
Ctrl-C
on the console) when you give a
continue
command. This allows you to break into the debugger again by pressing
Ctrl-C
. If you want Pdb not to touch the SIGINT handler, set
nosigint
to true.
范例调用启用跟踪采用 skip :
import pdb; pdb.Pdb(skip=['django.*']).set_trace()
3.1 版新增： The skip 自变量。
3.2 版新增： The nosigint 自变量。先前，Pdb 从不设置 SIGINT 处理程序。
run
(
语句
,
globals=None
,
locals=None
)
¶
runeval
(
表达式
,
globals=None
,
locals=None
)
¶
runcall
(
function
,
*args
,
**kwds
)
¶
set_trace
(
)
¶
See the documentation for the functions explained above.
The commands recognized by the debugger are listed below. Most commands can be abbreviated to one or two letters as indicated; 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.
调试器支持 aliases . Aliases can have parameters which allows one a certain level of adaptability to the context under examination.
Multiple commands may be entered on a single line, separated by
;;
。(单
;
is not used as it is the separator for multiple commands in a line that is passed to the Python parser.) No intelligence is applied to separating the commands; the input is split at the first
;;
pair, even if it is in the middle of a quoted string.
若文件
.pdbrc
exists in the user’s home directory or in the current directory, it is read in and executed as if it had been typed at the debugger prompt. This is particularly useful for aliases. If both files exist, the one in the home directory is read first and aliases defined there can be overridden by the local file.
3.2 版改变：
.pdbrc
现在可以包含继续调试命令，譬如
continue
or
next
. Previously, these commands had no effect.
h(elp)
[command]
¶
Without argument, print the list of available commands. With a
命令
as argument, print help about that command.
help pdb
displays the full documentation (the docstring of the
pdb
module). Since the
命令
argument must be an identifier,
help exec
must be entered to get help on the
!
命令。
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)
[count]
¶
移动当前帧 count (default one) levels down in the stack trace (to a newer frame).
u(p)
[count]
¶
移动当前帧 count (default one) levels up in the stack trace (to an older frame).
b(reak)
[([filename:]lineno | function) [, condition]]
¶
With a
lineno
argument, set a break there in the current file. With a
function
argument, set a break at the first executable statement within that function. The line number may be prefixed with a filename and a colon, to specify a breakpoint in another file (probably one that hasn’t been loaded yet). The file is searched on
sys.path
. Note that each breakpoint is assigned a number to which all the other breakpoint commands refer.
If a second argument is present, it is an expression which must evaluate to true before the breakpoint is honored.
Without argument, list all breaks, including for each breakpoint, the number of times that breakpoint has been hit, the current ignore count, and the associated condition if any.
tbreak
[([filename:]lineno | function) [, condition]]
¶
Temporary breakpoint, which is removed automatically when it is first hit. The arguments are the same as for
break
.
cl(ear)
[filename:lineno | bpnumber [bpnumber ...]]
¶
With a filename:lineno argument, clear all the breakpoints at this line. With a space separated list of breakpoint numbers, clear those breakpoints. Without argument, clear all breaks (but first ask confirmation).
disable
[bpnumber [bpnumber ...]]
¶
Disable the breakpoints given as a space separated list of breakpoint numbers. Disabling a breakpoint means it cannot cause the program to stop execution, but unlike clearing a breakpoint, it remains in the list of breakpoints and can be (re-)enabled.
enable
[bpnumber [bpnumber ...]]
¶
Enable the breakpoints specified.
ignore
bpnumber [count]
¶
Set the ignore count for the given breakpoint number. If count is omitted, the ignore count is set to 0. A breakpoint becomes active when the ignore count is zero. When non-zero, the count is decremented each time the breakpoint is reached and the breakpoint is not disabled and any associated condition evaluates to true.
条件
bpnumber [condition]
¶
Set a new 条件 for the breakpoint, an expression which must evaluate to true before the breakpoint is honored. If 条件 is absent, any existing condition is removed; i.e., the breakpoint is made unconditional.
命令
[bpnumber]
¶
指定命令列表为断点编号
bpnumber
. The commands themselves appear on the following lines. Type a line containing just
end
to terminate the commands. An example:
(Pdb) commands 1 (com) p some_variable (com) end (Pdb)
To remove all commands from a breakpoint, type commands and follow it immediately with
end
; that is, give no commands.
不带 bpnumber argument, commands refers to the last breakpoint set.
You can use breakpoint commands to start your program up again. Simply use the continue command, or step, or any other command that resumes execution.
Specifying any command resuming execution (currently continue, step, next, return, jump, quit and their abbreviations) terminates the command list (as if that command was immediately followed by end). This is because any time you resume execution (even with a simple next or step), you may encounter another breakpoint—which could have its own command list, leading to ambiguities about which list to execute.
If you use the ‘silent’ command in the command list, the usual message about stopping at a breakpoint is not printed. This may be desirable for breakpoints that are to print a specific message and then continue. If none of the other commands print anything, you see no sign that the breakpoint was reached.
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.)
unt(il)
[lineno]
¶
Without argument, continue execution until the line with a number greater than the current one is reached.
With a line number, continue execution until a line with a number greater or equal to that is reached. In both cases, also stop when the current frame returns.
3.2 版改变： 允许给出明确行号。
r(eturn)
¶
继续执行，直到当前函数返回为止。
c(ont(inue))
¶
Continue execution, only stop when a breakpoint is encountered.
j(ump)
lineno
¶
Set the next line that will be executed. Only available in the bottom-most frame. This lets you jump back and execute code again, or jump forward to skip code that you don’t want to run.
It should be noted that not all jumps are allowed – for instance it is not possible to jump into the middle of a
for
loop or out of a
finally
子句。
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
.
as argument, list 11 lines around the current line. 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.
The current line in the current frame is indicated by
->
. If an exception is being debugged, the line where the exception was originally raised or propagated is indicated by
>>
, if it differs from the current line.
3.2 版新增：
The
>>
标记。
ll
| longlist
¶
List all source code for the current function or frame. Interesting lines are marked as for
list
.
3.2 版新增。
a(rgs)
¶
Print the argument list of the current function.
p
表达式
¶
评估 表达式 in the current context and print its value.
注意
print()
can also be used, but is not a debugger command — this executes the Python
print()
函数。
whatis
表达式
¶
打印类型为 表达式 .
source
表达式
¶
Try to get source code for the given object and display it.
3.2 版新增。
display
[expression]
¶
Display the value of the expression if it changed, each time execution stops in the current frame.
Without expression, list all display expressions for the current frame.
3.2 版新增。
undisplay
[expression]
¶
Do not display the expression any more in the current frame. Without expression, clear all display expressions for the current frame.
3.2 版新增。
interact
¶
启动交互解释器 (使用
code
module) whose global namespace contains all the (global and local) names found in the current scope.
3.2 版新增。
alias
[name [command]]
¶
创建别名称为
name
执行
命令
。命令必须
not
be enclosed in quotes. Replaceable parameters can be indicated by
%1
,
%2
, and so on, while
%*
is replaced by all the parameters. If no command is given, the current alias for
name
is shown. If no arguments are given, all aliases are listed.
Aliases may be nested and can contain anything that can be legally typed at the pdb prompt. Note that internal pdb commands can be overridden by aliases. Such a command is then hidden until the alias is removed. Aliasing is recursively applied to the first word of the command line; all other words in the line are left alone.
As an example, here are two useful aliases (especially when placed in the
.pdbrc
file):
# Print instance variables (usage "pi classInst") alias pi for k in %1.__dict__.keys(): print("%1.",k,"=",%1.__dict__[k]) # Print instance variables in self alias ps pi self
unalias
名称
¶
删除指定别名。
!
语句
¶
执行 (1 行)
语句
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
statement on the same line, e.g.:
(Pdb) global list_options; list_options = ['-l'] (Pdb)
run
[args ...]
¶
restart
[args ...]
¶
Restart the debugged Python program. If an argument is supplied, it is split with
shlex
and the result is used as the new
sys.argv
. History, breakpoints, actions and debugger options are preserved.
restart
是别名化的
run
.
q(uit)
¶
从调试器离开。中止正执行程序。
脚注
| [1] |
Whether a frame is considered to originate in a certain module
is determined by the
__name__
in the frame globals.
|