1. Xavier de Gaye
  2. pyclewn



A Vim front-end to the gdb and pdb debuggers. The debugger output is redirected to a Vim window, the console. The debugger commands are mapped to Vim user-defined commands and completion is available on Vim command line.

Install Pyclewn with pip and extract a vimball from the installed Python package, then install the Vim runtime files with the vimball. See install.


  • When Pyclewn is started from gvim with the :Pyclewn command, the :Cinferiortty command may be used to launch a terminal connected to a pseudo terminal that becomes the controlling terminal of the program being debugged by gdb or by pdb.
  • A debugger command can be mapped in Vim to a key sequence using Vim key mappings. This allows, for example, to set/clear a breakpoint or print a variable value at the current cursor or mouse position by just hitting a key.
  • Breakpoints and the line in the current frame are highlighted in the source code. Disabled breakpoints are noted with a different highlighting color. Pyclewn automatically finds the source file for the breakpoint if it exists, and tells Vim to load and display the file and highlight the line.
  • Multiple consecutive Pyclewn sessions can be started from gvim with the :Pyclewn command.
  • The value of an expression or variable is displayed in a balloon in gvim when the mouse pointer is hovering over the selected expression or the variable.


  • Full gdb completion on Vim command line.
  • An expression can be watched in a Vim window. The expression value is updated and highlighted whenever it has changed. When the expression is a structure or class instance, it can be expanded (resp. folded) to show (resp. hide) its members and their values.
  • Three Vim buffers are updated by gdb, they list the breakpoints, the backtrace and the threads. One can jump with the <CR> key or the mouse to the corresponding source code line from the (clewn)_breakpoints window or switch to the corresponding frame from the (clewn)_backtrace window, or switch to the correponding thread with the (clewn)_threads window.
  • A sequence of gdb commands can be run from a Vim script when the async option is set. This may be useful in a key mapping.
  • The project command saves the current gdb settings to a project file that may be sourced later by the gdb source command. These settings are the working directory, the debuggee program file name, the program arguments and the breakpoints. The sourcing and saving of the project file can be automated to occur on each gdb startup and termination, with the project command line option.


  • Pyclewn is a front-end to pdb-clone. With breakpoints Pyclewn runs just below the speed of the Python interpreter (the command line Python debugger, pdb, runs 10 to 100 times slower than the interpreter).
  • Similarly to gdb, one may attach to a running Python process with the pdb debugger, interrupt the process, manage a debugging session and terminate the debugging session by detaching from the process. A new debugging session may be conducted later on this same process, possibly from another Vim instance.


  • platforms
    • All unix platforms supported by Python.
    • GNU gdb from macports is required on Mac Os X.
  • languages
    • Python 2.7 or Python >= 3.2.
    • C language for the _bdb extension module of pdb-clone.
  • Vim
    • gvim 7.0 and above.
    • vim 7.3 or above (vim in a terminal).
    • pyclewn is a standalone program connected to Vim with a netbeans socket, that may be started from Vim with the :Pyclewn command since Vim 7.3.
  • gdb
    • gdb/mi interface.
    • Asynchronous gdb commands.
    • The watched variables, breakpoints, backtrace and threads windows.
    • The project file.
  • pdb
    • Interrupt the debuggee.
    • Attach to a running Python process.
    • The threadstack command.


This software is licensed under the GNU General Public License Version 2. Pdb-clone is a derivative work of a part of Python and as such, subject to the Python license.