Merge pull request #478 from python-cmd2/hook_example

Add hook example

Author: tleonhardt

examples/hooks.py

@@ -0,0 +1,115 @@
+#!/usr/bin/env python
+# coding=utf-8
+"""
+A sample application for cmd2 demonstrating how to use hooks.
+
+This application shows how to use postparsing hooks to allow case insensitive
+command names, abbreviated commands, as well as allowing numeric arguments to
+follow a command without any intervening whitespace.
+
+"""
+
+import re
+
+from typing import List
+
+import cmd2
+
+
+class CmdLineApp(cmd2.Cmd):
+    """Example cmd2 application demonstrating the use of hooks.
+
+    This simple application has one command, `list` which generates a list
+    of 10 numbers. This command takes one optional argument, which is the
+    number to start on.
+
+    We have three postparsing hooks, which allow the user to enter:
+
+        (Cmd) list 5
+        (Cmd) L 5
+        (Cmd) l 5
+        (Cmd) L5
+        (Cmd) LI5
+
+    and have them all treated as valid input which prints a list of 10 numbers
+    starting with the number 5.
+    """
+
+    # Setting this true makes it run a shell command if a cmd2/cmd command doesn't exist
+    # default_to_shell = True
+    def __init__(self, *args, **kwargs):
+        # sneakily remove the cmd2.Cmd command called load
+        # this lets a user enter a command like "l5" and allows it to
+        # be unambiguous
+        delattr(cmd2.Cmd, "do_load")
+
+        super().__init__(*args, **kwargs)
+
+        # register three hooks
+        self.register_postparsing_hook(self.add_whitespace_hook)
+        self.register_postparsing_hook(self.downcase_hook)
+        self.register_postparsing_hook(self.abbrev_hook)
+
+    def add_whitespace_hook(self, data: cmd2.plugin.PostparsingData) -> cmd2.plugin.PostparsingData:
+        """A hook to split alphabetic command names immediately followed by a number.
+
+        l24 -> l 24
+        list24 -> list 24
+        list 24 -> list 24
+
+        """
+        command = data.statement.command
+        # regular expression with looks for:
+        #  ^ - the beginning of the string
+        # ([^\s\d]+) - one or more non-whitespace non-digit characters, set as capture group 1
+        # (\d+) - one or more digit characters, set as capture group 2
+        command_pattern = re.compile(r'^([^\s\d]+)(\d+)')
+        match = command_pattern.search(command)
+        if match:
+            data.statement = self.statement_parser.parse("{} {} {}".format(
+                match.group(1),
+                match.group(2),
+                '' if data.statement.args is None else data.statement.args
+            ))
+        return data
+
+    def downcase_hook(self, data: cmd2.plugin.PostparsingData) -> cmd2.plugin.PostparsingData:
+        """A hook to make uppercase commands lowercase."""
+        command = data.statement.command.lower()
+        data.statement = self.statement_parser.parse("{} {}".format(
+            command,
+            '' if data.statement.args is None else data.statement.args
+        ))
+        return data
+
+    def abbrev_hook(self, data: cmd2.plugin.PostparsingData) -> cmd2.plugin.PostparsingData:
+        """Accept unique abbreviated commands"""
+        target = 'do_' + data.statement.command
+        if target not in dir(self):
+            # check if the entered command might be an abbreviation
+            funcs = [func for func in self.keywords if func.startswith(data.statement.command)]
+            if len(funcs) == 1:
+                raw = data.statement.raw.replace(data.statement.command, funcs[0], 1)
+                data.statement = self.statement_parser.parse(raw)
+        return data
+
+    @cmd2.with_argument_list
+    def do_list(self, arglist: List[str]) -> None:
+        """Generate a list of 10 numbers."""
+        if arglist:
+            first = arglist[0]
+            try:
+                first = int(first)
+            except ValueError:
+                first = 1
+        else:
+            first = 1
+        last = first + 10
+
+        for x in range(first, last):
+            self.poutput(str(x))
+
+
+if __name__ == '__main__':
+    c = CmdLineApp()
+    c.cmdloop()