source: python/vendor/Python-2.7.6/Lib/idlelib/CallTips.py

"""CallTips.py - An IDLE Extension to Jog Your Memory

Call Tips are floating windows which display function, class, and method
parameter and docstring information when you type an opening parenthesis, and
which disappear when you type a closing parenthesis.

"""
import re
import sys
import types

from idlelib import CallTipWindow
from idlelib.HyperParser import HyperParser

import __main__

class CallTips:

    menudefs = [
        ('edit', [
            ("Show call tip", "<<force-open-calltip>>"),
        ])
    ]

    def __init__(self, editwin=None):
        if editwin is None:  # subprocess and test
            self.editwin = None
            return
        self.editwin = editwin
        self.text = editwin.text
        self.calltip = None
        self._make_calltip_window = self._make_tk_calltip_window

    def close(self):
        self._make_calltip_window = None

    def _make_tk_calltip_window(self):
        # See __init__ for usage
        return CallTipWindow.CallTip(self.text)

    def _remove_calltip_window(self, event=None):
        if self.calltip:
            self.calltip.hidetip()
            self.calltip = None

    def force_open_calltip_event(self, event):
        """Happens when the user really wants to open a CallTip, even if a
        function call is needed.
        """
        self.open_calltip(True)

    def try_open_calltip_event(self, event):
        """Happens when it would be nice to open a CallTip, but not really
        necessary, for example after an opening bracket, so function calls
        won't be made.
        """
        self.open_calltip(False)

    def refresh_calltip_event(self, event):
        """If there is already a calltip window, check if it is still needed,
        and if so, reload it.
        """
        if self.calltip and self.calltip.is_active():
            self.open_calltip(False)

    def open_calltip(self, evalfuncs):
        self._remove_calltip_window()

        hp = HyperParser(self.editwin, "insert")
        sur_paren = hp.get_surrounding_brackets('(')
        if not sur_paren:
            return
        hp.set_index(sur_paren[0])
        expression = hp.get_expression()
        if not expression or (not evalfuncs and expression.find('(') != -1):
            return
        arg_text = self.fetch_tip(expression)
        if not arg_text:
            return
        self.calltip = self._make_calltip_window()
        self.calltip.showtip(arg_text, sur_paren[0], sur_paren[1])

    def fetch_tip(self, expression):
        """Return the argument list and docstring of a function or class

        If there is a Python subprocess, get the calltip there.  Otherwise,
        either fetch_tip() is running in the subprocess itself or it was called
        in an IDLE EditorWindow before any script had been run.

        The subprocess environment is that of the most recently run script.  If
        two unrelated modules are being edited some calltips in the current
        module may be inoperative if the module was not the last to run.

        To find methods, fetch_tip must be fed a fully qualified name.

        """
        try:
            rpcclt = self.editwin.flist.pyshell.interp.rpcclt
        except AttributeError:
            rpcclt = None
        if rpcclt:
            return rpcclt.remotecall("exec", "get_the_calltip",
                                     (expression,), {})
        else:
            entity = self.get_entity(expression)
            return get_arg_text(entity)

    def get_entity(self, expression):
        """Return the object corresponding to expression evaluated
        in a namespace spanning sys.modules and __main.dict__.
        """
        if expression:
            namespace = sys.modules.copy()
            namespace.update(__main__.__dict__)
            try:
                return eval(expression, namespace)
            except BaseException:
                # An uncaught exception closes idle, and eval can raise any
                # exception, especially if user classes are involved.
                return None

def _find_constructor(class_ob):
    # Given a class object, return a function object used for the
    # constructor (ie, __init__() ) or None if we can't find one.
    try:
        return class_ob.__init__.im_func
    except AttributeError:
        for base in class_ob.__bases__:
            rc = _find_constructor(base)
            if rc is not None: return rc
    return None

def get_arg_text(ob):
    """Get a string describing the arguments for the given object,
       only if it is callable."""
    arg_text = ""
    if ob is not None and hasattr(ob, '__call__'):
        arg_offset = 0
        if type(ob) in (types.ClassType, types.TypeType):
            # Look for the highest __init__ in the class chain.
            fob = _find_constructor(ob)
            if fob is None:
                fob = lambda: None
            else:
                arg_offset = 1
        elif type(ob)==types.MethodType:
            # bit of a hack for methods - turn it into a function
            # but we drop the "self" param.
            fob = ob.im_func
            arg_offset = 1
        else:
            fob = ob
        # Try to build one for Python defined functions
        if type(fob) in [types.FunctionType, types.LambdaType]:
            argcount = fob.func_code.co_argcount
            real_args = fob.func_code.co_varnames[arg_offset:argcount]
            defaults = fob.func_defaults or []
            defaults = list(map(lambda name: "=%s" % repr(name), defaults))
            defaults = [""] * (len(real_args) - len(defaults)) + defaults
            items = map(lambda arg, dflt: arg + dflt, real_args, defaults)
            if fob.func_code.co_flags & 0x4:
                items.append("...")
            if fob.func_code.co_flags & 0x8:
                items.append("***")
            arg_text = ", ".join(items)
            arg_text = "(%s)" % re.sub("(?<!\d)\.\d+", "<tuple>", arg_text)
        # See if we can use the docstring
        doc = getattr(ob, "__doc__", "")
        if doc:
            doc = doc.lstrip()
            pos = doc.find("\n")
            if pos < 0 or pos > 70:
                pos = 70
            if arg_text:
                arg_text += "\n"
            arg_text += doc[:pos]
    return arg_text

#################################################
#
# Test code
#
if __name__=='__main__':

    def t1(): "()"
    def t2(a, b=None): "(a, b=None)"
    def t3(a, *args): "(a, ...)"
    def t4(*args): "(...)"
    def t5(a, *args): "(a, ...)"
    def t6(a, b=None, *args, **kw): "(a, b=None, ..., ***)"
    def t7((a, b), c, (d, e)): "(<tuple>, c, <tuple>)"

    class TC(object):
        "(ai=None, ...)"
        def __init__(self, ai=None, *b): "(ai=None, ...)"
        def t1(self): "()"
        def t2(self, ai, b=None): "(ai, b=None)"
        def t3(self, ai, *args): "(ai, ...)"
        def t4(self, *args): "(...)"
        def t5(self, ai, *args): "(ai, ...)"
        def t6(self, ai, b=None, *args, **kw): "(ai, b=None, ..., ***)"
        def t7(self, (ai, b), c, (d, e)): "(<tuple>, c, <tuple>)"

    def test(tests):
        ct = CallTips()
        failed=[]
        for t in tests:
            expected = t.__doc__ + "\n" + t.__doc__
            name = t.__name__
            # exercise fetch_tip(), not just get_arg_text()
            try:
                qualified_name = "%s.%s" % (t.im_class.__name__, name)
            except AttributeError:
                qualified_name = name
            arg_text = ct.fetch_tip(qualified_name)
            if arg_text != expected:
                failed.append(t)
                fmt = "%s - expected %s, but got %s"
                print  fmt % (t.__name__, expected, get_arg_text(t))
        print "%d of %d tests failed" % (len(failed), len(tests))

    tc = TC()
    tests = (t1, t2, t3, t4, t5, t6, t7,
             TC, tc.t1, tc.t2, tc.t3, tc.t4, tc.t5, tc.t6, tc.t7)

    # test(tests)
    from unittest import main
    main('idlelib.idle_test.test_calltips', verbosity=2, exit=False)