CODEWITHSUNDEEP
python
MiddleClassMan
MiddleClassMan

Reputation: 31

Coding a shell in Python

I am coding a data entry system in Python, in which the user should also be able to submit 'commands', exactly like the Python shell works, or for example SAS or R interfaces. I would like to know how to code a shell. For examnple, it should provide a prompt (which cannot be deleted by the user, e.g. the >>> prompt in Python) and receive input from the user. Furthermore, once an entry is submitted, the user cannot go back, like in the DOS prompt, where you cannot go up a line, so to speak.

Can anybody help with this?

Upvotes: 0

Views: 304

Answers (3)

Jeff LaFay
Jeff LaFay

Reputation: 13350

The cmd.Cmd class is something that would help you build a shell-like application. Likewise, cmd2 is a nice upgrade from the above module. With these you can build a shell application that has command history, help menus, and smart command parsing. Don't build a REPL from scratch because these modules will probably suffice for your needs.

Upvotes: 5

themel
themel

Reputation: 8895

You might want to look into the readline library (gets you fancy features like completion and history as well). Sadly, it's UNIX only, like it's underlying C library.

Upvotes: 0

Blender
Blender

Reputation: 298196

I coded a whole sh implementation in Python a while back, but sadly I don't have the source.

Your basic code would be this:

while True:
  command = raw_input('>>> ')
  print 'You entered "{command}".'.format(command = command)

But if you need something more complicated than a simple bash-like shell, there are a few projects that might suit your needs:

  • IPython: Pretty solid shell. It's used by Sage and a bunch of other big projects.
  • Python's native cmd class: self explanatory. Not very feature rich, but it's the Python shell.

Upvotes: 0

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