Multichoicebox now able to accept multiple preselects

Addresses Issue 92.   This should do as requested.  You can set
preselect to None (actually that might have been possible before).  You
can also set to a list of selections for the multichoice case.

easygui/boxes/choice_box.py

@@ -1,3 +1,4 @@
+import collections
 import string
 
 try:
@@ -25,6 +26,7 @@ def choicebox(msg="Pick an item", title="", choices=[], preselect=0,
     :param str msg: the msg to be displayed
     :param str title: the window title
     :param list choices: a list or tuple of the choices to be displayed
+    :param preselect: Which item, if any are preselected when dialog appears
     :return: List containing choice selected or None if cancelled
     """
     mb = ChoiceBox(msg, title, choices, preselect=preselect,
@@ -53,6 +55,36 @@ def multchoicebox(msg="Pick an item", title="", choices=[],
         return mb
 
 
+# Utility function.  But, is it generic enough to be moved out of here?
+def make_list_or_none(obj, cast_type=None):
+    # -------------------------------------------------------------------
+    # for an object passed in, put it in standardized form.
+    # It may be None.  Just return None
+    # If it is a scalar, attempt to cast it into cast_type.  Raise error
+    # if not possible.  Convert scalar to a single-element list.
+    # If it is a collections.Sequence (including a scalar converted to let),
+    # then cast each element to cast_type.  Raise error if any cannot be converted. 
+    # -------------------------------------------------------------------
+    ret_val = obj
+    if ret_val is None:
+        return None
+    # Convert any non-sequence to single-element list
+    if not isinstance(obj, collections.Sequence):
+        if cast_type is not None:
+            try:
+                ret_val = cast_type(obj)
+            except Exception, e:
+                raise Exception("Value {} cannot be converted to type: {}".format(obj, cast_type))
+        ret_val = [ret_val,]
+    # Convert all elements to cast_type
+    if cast_type is not None:
+        try:
+            ret_val = [cast_type(elem) for elem in ret_val]
+        except:
+            raise Exception("Not all values in {}\n can be converted to type: {}".format(ret_val, cast_type))
+    return ret_val
+
+
 class ChoiceBox(object):
 
     def __init__(self, msg, title, choices, preselect, multiple_select, callback):
@@ -61,7 +93,12 @@ def __init__(self, msg, title, choices, preselect, multiple_select, callback):
 
         self.choices = self.to_list_of_str(choices)
 
-        self.ui = GUItk(msg, title, self.choices, preselect, multiple_select,
+        # Convert preselect to always be a list or None.
+        preselect_list = make_list_or_none(preselect, cast_type=int)
+        if not multiple_select and len(preselect_list)>1:
+            raise ValueError("Multiple selections not allowed, yet preselect has multiple values:{}".format(preselect_list))
+
+        self.ui = GUItk(msg, title, self.choices, preselect_list, multiple_select,
                         self.callback_ui)
 
     def run(self):
@@ -125,6 +162,7 @@ def to_list_of_str(self, choices):
 
         return choices
 
+
 
 class GUItk(object):
 
@@ -168,7 +206,7 @@ def __init__(self, msg, title, choices, preselect, multiple_select, callback):
         self.create_cancel_button()
 
         self. create_special_buttons()
-
+        
         self.preselect_choice(preselect)
 
         self.choiceboxWidget.focus_force()
@@ -233,9 +271,11 @@ def get_pos(self):
         global_state.window_position = '+' + geom.split('+', 1)[1]
 
     def preselect_choice(self, preselect):
+        print(preselect)
         if preselect != None:
-            self.choiceboxWidget.select_set(preselect)
-            self.choiceboxWidget.activate(preselect)
+            for v in preselect:
+                self.choiceboxWidget.select_set(v)
+                self.choiceboxWidget.activate(v)
 
     def get_choices(self):
         choices_index = self.choiceboxWidget.curselection()

easygui/boxes/demo.py

@@ -212,9 +212,9 @@ def demo_multichoicebox():
                    "jjj", "kkk", "LLL", "mmm", "nnn", "ooo",
                    "ppp", "qqq", "rrr", "sss", "ttt", "uuu",
                    "vvv"]
-
+    preselect = None #[0, 2, 4]
     msg = "Pick as many choices as you wish."
-    reply = multchoicebox(msg, "Demo of multchoicebox", listChoices)
+    reply = multchoicebox(msg, "Demo of multchoicebox", listChoices, preselect)
     print("Reply was: {!r}".format(reply))
     return reply