# 9.1 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).

u(p)

  Move the current frame one level up in the stack trace (to a newer frame).

b(reak) [lineno`|`function] [, "condition"]

  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. 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.

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.