PDT: Refactor per Pylint suggestions + readability

- Remove unused imports
- Add comments where appropriate
- Improve readability of variable names
- Re-implement a couple of functions using dictionaries instead of if-statements
- Results of Pylint & Black operations, plus some fixes to code.

1 files changed, 131 insertions, 125 deletions

diff --git a/precision_drawing_tools/pdt_msg_strings.py b/precision_drawing_tools/pdt_msg_strings.py
index 950e8661..a9246fce 100644
--- a/precision_drawing_tools/pdt_msg_strings.py
+++ b/precision_drawing_tools/pdt_msg_strings.py
@@ -28,147 +28,153 @@
 #
 # Menu Labels
 #
-PDT_LAB_ABS           = "Absolute"    # "Global"
-PDT_LAB_DEL           = "Delta"       # "Relative"
-PDT_LAB_DIR           = "Direction"   # "Polar"
-PDT_LAB_NOR           = "Normal"      # "Perpendicular"
-PDT_LAB_ARCCENTRE     = "Arc Centre"
-PDT_LAB_PLANE         = "Plane"
-PDT_LAB_MODE          = "Mode"
-PDT_LAB_OPERATION     = "Operation"
-PDT_LAB_PERCENT       = "Percent"
-PDT_LAB_INTERSECT     = "Intersect"   # "Convergance"
-PDT_LAB_ORDER         = "Order"
-PDT_LAB_FLIPANGLE     = "Flip Angle"
-PDT_LAB_FLIPPERCENT   = "Flip %"
-PDT_LAB_ALLACTIVE     = "All/Active"
-PDT_LAB_VARIABLES     = "Coordinates/Delta Offsets & Other Variables"
-PDT_LAB_CVALUE        = "Coordinates"
-PDT_LAB_DISVALUE      = "Distance"
-PDT_LAB_ANGLEVALUE    = "Angle"
-PDT_LAB_PERCENTS      = "%"
-PDT_LAB_TOOLS         = "Tools"
-PDT_LAB_JOIN2VERTS    = "Join 2 Verts"
-PDT_LAB_ORIGINCURSOR  = "Origin To Cursor"
-PDT_LAB_AD2D          = "Set A/D 2D"
-PDT_LAB_AD3D          = "Set A/D 3D"
-PDT_LAB_TAPERAXES     = ""            # Intentionally left blank
-PDT_LAB_TAPER         = "Taper"
-PDT_LAB_INTERSETALL   = "Intersect All"
-PDT_LAB_BISECT        = "Bisect"
-PDT_LAB_EDGETOEFACE   = "Edge-To-Face"
-PDT_LAB_FILLET        = "Fillet"
-PDT_LAB_SEGMENTS      = "Segments"
-PDT_LAB_USEVERTS      = "Use Vertices"
-PDT_LAB_RADIUS        = "Radius"
-PDT_LAB_PROFILE       = "Profile"
-PDT_LAB_PIVOTSIZE     = ""            # Intentionally left blank
-PDT_LAB_PIVOTWIDTH    = ""            # Intentionally left blank
-PDT_LAB_PIVOTALPHA    = ""            # Intentionally left blank
-PDT_LAB_PIVOTLOC      = ""            # Intentionally left blank
-PDT_LAB_PIVOTLOCH     = "Location"
+PDT_LAB_ABS = "Absolute"  # "Global"
+PDT_LAB_DEL = "Delta"  # "Relative"
+PDT_LAB_DIR = "Direction"  # "Polar"
+PDT_LAB_NOR = "Normal"  # "Perpendicular"
+PDT_LAB_ARCCENTRE = "Arc Centre"
+PDT_LAB_PLANE = "Plane"
+PDT_LAB_MODE = "Mode"
+PDT_LAB_OPERATION = "Operation"
+PDT_LAB_PERCENT = "Percent"
+PDT_LAB_INTERSECT = "Intersect"  # "Convergance"
+PDT_LAB_ORDER = "Order"
+PDT_LAB_FLIPANGLE = "Flip Angle"
+PDT_LAB_FLIPPERCENT = "Flip %"
+PDT_LAB_ALLACTIVE = "All/Active"
+PDT_LAB_VARIABLES = "Coordinates/Delta Offsets & Other Variables"
+PDT_LAB_CVALUE = "Coordinates"
+PDT_LAB_DISVALUE = "Distance"
+PDT_LAB_ANGLEVALUE = "Angle"
+PDT_LAB_PERCENTS = "%"
+PDT_LAB_TOOLS = "Tools"
+PDT_LAB_JOIN2VERTS = "Join 2 Verts"
+PDT_LAB_ORIGINCURSOR = "Origin To Cursor"
+PDT_LAB_AD2D = "Set A/D 2D"
+PDT_LAB_AD3D = "Set A/D 3D"
+PDT_LAB_TAPERAXES = ""  # Intentionally left blank
+PDT_LAB_TAPER = "Taper"
+PDT_LAB_INTERSETALL = "Intersect All"
+PDT_LAB_BISECT = "Bisect"
+PDT_LAB_EDGETOEFACE = "Edge-To-Face"
+PDT_LAB_FILLET = "Fillet"
+PDT_LAB_SEGMENTS = "Segments"
+PDT_LAB_USEVERTS = "Use Vertices"
+PDT_LAB_RADIUS = "Radius"
+PDT_LAB_PROFILE = "Profile"
+PDT_LAB_PIVOTSIZE = ""  # Intentionally left blank
+PDT_LAB_PIVOTWIDTH = ""  # Intentionally left blank
+PDT_LAB_PIVOTALPHA = ""  # Intentionally left blank
+PDT_LAB_PIVOTLOC = ""  # Intentionally left blank
+PDT_LAB_PIVOTLOCH = "Location"
 #
 # Error Message
 #
-PDT_ERR_NO_ACT_OBJ    = "No Active Object - Please Select an Object"
-PDT_OBJ_MODE_ERROR    = "Only Mesh Object in Edit or Object Mode Supported"
-PDT_ERR_NO_ACT_VERT   = "No Active Vertex - Select One Vertex Individually"
-PDT_ERR_NO_SEL_GEOM   = "No Geometry/Objects Selected"
-PDT_ERR_NO_ACT_VERTS  = "No Selected Geometry - Please Select some Geometry"
-PDT_ERR_NON_VALID     = "is Not a Valid Option in Selected Object's Mode for Command:"
-PDT_ERR_VERT_MODE     = "Work in Vertex Mode for this Function"
-PDT_ERR_NOPPLOC       = "Custom Property PDT_PP_LOC for this object not found, have you Written it yet?"
-PDT_ERR_NO_LIBRARY    = "PDT Library Blend File (parts_library.blend) is Missing from Addons/clockworxpdt Folder"
+PDT_ERR_NO_ACT_OBJ = "No Active Object - Please Select an Object"
+PDT_OBJ_MODE_ERROR = "Only Mesh Object in Edit or Object Mode Supported"
+PDT_ERR_NO_ACT_VERT = "No Active Vertex - Select One Vertex Individually"
+PDT_ERR_NO_SEL_GEOM = "No Geometry/Objects Selected"
+PDT_ERR_NO_ACT_VERTS = "No Selected Geometry - Please Select some Geometry"
+PDT_ERR_NON_VALID = "is Not a Valid Option in Selected Object's Mode for Command:"
+PDT_ERR_VERT_MODE = "Work in Vertex Mode for this Function"
+PDT_ERR_NOPPLOC = (
+    "Custom Property PDT_PP_LOC for this object not found, have you Written it yet?"
+)
+PDT_ERR_NO_LIBRARY = ("PDT Library Blend File (parts_library.blend) is Missing "
+                      + "from Addons/clockworxpdt Folder")
 
-PDT_ERR_SEL_1_VERTI   = "Select at least 1 Vertex Individually (Currently selected:"
-PDT_ERR_SEL_1_VERT    = "Select at least 1 Vertex (Currently selected:"
-PDT_ERR_SEL_2_VERTI   = "Select at least 2 Vertices Individually (Currently selected:"
-PDT_ERR_SEL_2_VERTIO  = "Select Exactly 2 Vertices Individually (Currently selected:"
-PDT_ERR_SEL_2_VERTS   = "Select Exactly 2 Vertices (Currently selected:"
-PDT_ERR_SEL_2_EDGES   = "Select Only 2 Non-Intersecting Edges (Currently selected:"
-PDT_ERR_SEL_3_VERTS   = "Select Exactly 3 Vertices (Currently selected:"
-PDT_ERR_SEL_3_VERTIO  = "Select Exactly 3 Vertices Individually (Currently selected:"
-PDT_ERR_SEL_2_V_1_E   = "Select 2 Vertices Individually, or 1 Edge (Currently selected:"
-PDT_ERR_SEL_4_VERTS   = "Select 4 Vertices Individually, or 2 Edges (Currently selected:"
-PDT_ERR_SEL_1_E_1_F   = "Select 1 Face and 1 Detached Edge"
+PDT_ERR_SEL_1_VERTI = "Select at least 1 Vertex Individually (Currently selected:"
+PDT_ERR_SEL_1_VERT = "Select at least 1 Vertex (Currently selected:"
+PDT_ERR_SEL_2_VERTI = "Select at least 2 Vertices Individually (Currently selected:"
+PDT_ERR_SEL_2_VERTIO = "Select Exactly 2 Vertices Individually (Currently selected:"
+PDT_ERR_SEL_2_VERTS = "Select Exactly 2 Vertices (Currently selected:"
+PDT_ERR_SEL_2_EDGES = "Select Only 2 Non-Intersecting Edges (Currently selected:"
+PDT_ERR_SEL_3_VERTS = "Select Exactly 3 Vertices (Currently selected:"
+PDT_ERR_SEL_3_VERTIO = "Select Exactly 3 Vertices Individually (Currently selected:"
+PDT_ERR_SEL_2_V_1_E = "Select 2 Vertices Individually, or 1 Edge (Currently selected:"
+PDT_ERR_SEL_4_VERTS = "Select 4 Vertices Individually, or 2 Edges (Currently selected:"
+PDT_ERR_SEL_1_E_1_F = "Select 1 Face and 1 Detached Edge"
 
-PDT_ERR_SEL_1_EDGE    = "Select Exactly 1 Edge (Currently selected:"
-PDT_ERR_SEL_1_EDGEM   = "Select at least 1 Edge (Currently selected:"
+PDT_ERR_SEL_1_EDGE = "Select Exactly 1 Edge (Currently selected:"
+PDT_ERR_SEL_1_EDGEM = "Select at least 1 Edge (Currently selected:"
 
-PDT_ERR_SEL_1_OBJ     = "Select Exactly 1 Object (Currently selected:"
-PDT_ERR_SEL_2_OBJS    = "Select Exactly 2 Objects (Currently selected:"
-PDT_ERR_SEL_3_OBJS    = "Select Exactly 3 Objects (Currently selected:"
-PDT_ERR_SEL_4_OBJS    = "Select Exactly 4 Objects (Currently selected:"
+PDT_ERR_SEL_1_OBJ = "Select Exactly 1 Object (Currently selected:"
+PDT_ERR_SEL_2_OBJS = "Select Exactly 2 Objects (Currently selected:"
+PDT_ERR_SEL_3_OBJS = "Select Exactly 3 Objects (Currently selected:"
+PDT_ERR_SEL_4_OBJS = "Select Exactly 4 Objects (Currently selected:"
 
-PDT_ERR_FACE_SEL      = "You have a Face Selected, this would have ruined the Topology"
+PDT_ERR_FACE_SEL = "You have a Face Selected, this would have ruined the Topology"
 
-PDT_ERR_INT_LINES     = "Implied Lines Do Not Intersect in"
-PDT_ERR_INT_NO_ALL    = "Active Vertex was not Closest to Intersection and All/Act was not Selected"
-PDT_ERR_STRIGHT_LINE  = "Selected Points all lie in a Straight Line"
-PDT_ERR_CONNECTED     = "Vertices are already Connected"
-PDT_ERR_EDIT_MODE     = "Only Works in EDIT Mode (Current mode:"
-PDT_ERR_EDOB_MODE     = "Only Works in EDIT, or OBJECT Modes (Current mode:"
-PDT_ERR_TAPER_ANG     = "Angle must be in Range -80 to +80 (Currently set to:"
-PDT_ERR_TAPER_SEL     = "Select at Least 2 Vertices Individually - Active is Rotation Point (Currently selected:"
-PDT_ERR_NO3DVIEW      = "View3D not found, cannot run operator"
-PDT_ERR_SCALEZERO     = "Scale Distance is 0"
+PDT_ERR_INT_LINES = "Implied Lines Do Not Intersect in"
+PDT_ERR_INT_NO_ALL = (
+    "Active Vertex was not Closest to Intersection and All/Act was not Selected"
+)
+PDT_ERR_STRIGHT_LINE = "Selected Points all lie in a Straight Line"
+PDT_ERR_CONNECTED = "Vertices are already Connected"
+PDT_ERR_EDIT_MODE = "Only Works in EDIT Mode (Current mode:"
+PDT_ERR_EDOB_MODE = "Only Works in EDIT, or OBJECT Modes (Current mode:"
+PDT_ERR_TAPER_ANG = "Angle must be in Range -80 to +80 (Currently set to:"
+PDT_ERR_TAPER_SEL = ("Select at Least 2 Vertices Individually - Active is Rotation Point "
+                     + "(Currently selected:")
+PDT_ERR_NO3DVIEW = "View3D not found, cannot run operator"
+PDT_ERR_SCALEZERO = "Scale Distance is 0"
 
-PDT_ERR_CHARS_NUM     = "Bad Command Format, not enough Characters"
-PDT_ERR_BADFLETTER    = "Bad Operator (1st Letter); C D E F G N M P S V or ? only"
-PDT_ERR_BADMATHS      = "Not a Valid Mathematical Expression!"
-PDT_ERR_BADCOORDL     = "X Y & Z Not permitted in anything other than Maths Operations"
-PDT_ERR_BAD1VALS      = "Bad Command - 1 Value needed"
-PDT_ERR_BAD2VALS      = "Bad Command - 2 Values needed"
-PDT_ERR_BAD3VALS      = "Bad Command - 3 Coords needed"
-PDT_ERR_ADDVEDIT      = "Only Add New Vertices in Edit Mode"
-PDT_ERR_SPLITEDIT     = "Only Split Edges in Edit Mode"
-PDT_ERR_EXTEDIT       = "Only Extrude Vertices in Edit Mode"
-PDT_ERR_DUPEDIT       = "Only Duplicate Geometry in Edit Mode"
-PDT_ERR_FILEDIT       = "Only Fillet Geometry in Edit Mode"
-PDT_ERR_NOCOMMAS      = "No commas allowed in Maths Command"
+PDT_ERR_CHARS_NUM = "Bad Command Format, not enough Characters"
+PDT_ERR_BADFLETTER = "Bad Operator (1st Letter); C D E F G N M P S V or ? only"
+PDT_ERR_BADMATHS = "Not a Valid Mathematical Expression!"
+PDT_ERR_BADCOORDL = "X Y & Z Not permitted in anything other than Maths Operations"
+PDT_ERR_BAD1VALS = "Bad Command - 1 Value needed"
+PDT_ERR_BAD2VALS = "Bad Command - 2 Values needed"
+PDT_ERR_BAD3VALS = "Bad Command - 3 Coords needed"
+PDT_ERR_ADDVEDIT = "Only Add New Vertices in Edit Mode"
+PDT_ERR_SPLITEDIT = "Only Split Edges in Edit Mode"
+PDT_ERR_EXTEDIT = "Only Extrude Vertices in Edit Mode"
+PDT_ERR_DUPEDIT = "Only Duplicate Geometry in Edit Mode"
+PDT_ERR_FILEDIT = "Only Fillet Geometry in Edit Mode"
+PDT_ERR_NOCOMMAS = "No commas allowed in Maths Command"
 
-PDT_ERR_2CPNPE        = "Select 2 Co-Planar Non-Parallel Edges"
-PDT_ERR_NCEDGES       = "Edges must be Co-Planar Non-Parallel Edges, Selected Edges aren't"
-PDT_ERR_1EDGE1FACE    = "Select 1 face and 1 Detached Edge"
-PDT_ERR_NOINT         = "No Intersection Found"
+PDT_ERR_2CPNPE = "Select 2 Co-Planar Non-Parallel Edges"
+PDT_ERR_NCEDGES = "Edges must be Co-Planar Non-Parallel Edges, Selected Edges aren't"
+PDT_ERR_1EDGE1FACE = "Select 1 face and 1 Detached Edge"
+PDT_ERR_NOINT = "No Intersection Found"
 
 # Info messages
 #
-PDT_INF_OBJ_MOVED     = "Active Object Moved to Intersection, "
+PDT_INF_OBJ_MOVED = "Active Object Moved to Intersection, "
 
 # Confirm Messages
 #
-PDT_CON_AREYOURSURE   = "Are You Sure About This?"
+PDT_CON_AREYOURSURE = "Are You Sure About This?"
 
 # Descriptions
 #
-PDT_DES_COORDS        = "Cartesian Inputs"
-PDT_DES_OFFDIS        = "Offset Distance"
-PDT_DES_OFFANG        = "Offset Angle"
-PDT_DES_OFFPER        = "Offset Percentage"
-PDT_DES_WORPLANE      = "Choose Working Plane"
-PDT_DES_MOVESEL       = "Select Move Mode"
-PDT_DES_OPMODE        = "Select Operation Mode"
-PDT_DES_ROTMOVAX      = "Rotational Axis - Movement Axis"
-PDT_DES_FLIPANG       = "Flip Angle 180 degrees"
-PDT_DES_FLIPPER       = "Flip Percent to 100 - %"
-PDT_DES_TRIM          = "Trim/Extend only Active Vertex, or All"
-PDT_DES_LIBOBS        = "Objects in Library"
-PDT_DES_LIBCOLS       = "Collections in Library"
-PDT_DES_LIBMATS       = "Materials in Library"
-PDT_DES_LIBMODE       = "Library Mode"
-PDT_DES_LIBSER        = "Enter A Search String (Contained)"
-PDT_DES_OBORDER       = "Object Order to Lines"
-PDT_DES_VALIDLET      = "Valid 1st letters; C D E G N P S V, Valid 2nd letters: A D I O P"
-PDT_DES_OUTPUT        = "Output for Maths Operations"
-PDT_DES_PPLOC         = "Location of PivotPoint"
-PDT_DES_PPSCALEFAC    = "Scale Factors"
-PDT_DES_PPSIZE        = "Pivot Size Factor"
-PDT_DES_PPWIDTH       = "Pivot Line Width in Pixels"
-PDT_DES_PPTRANS       = "Pivot Point Transparency"
-PDT_DES_PIVOTDIS      = "Input Distance to Compare with Sytem Distance to set Scales"
-PDT_DES_FILLETRAD     = "Fillet Radius"
-PDT_DES_FILLETSEG     = "Number of Fillet Segments"
-PDT_DES_FILLETPROF    = "Fillet Profile"
-PDT_DES_FILLETVERTS   = "Use Vertices, or Edges, Set to False for Extruded Geometry"
-PDT_DES_FILLINT       = "Intersect & Fillet Two Selected Edges"
+PDT_DES_COORDS = "Cartesian Inputs"
+PDT_DES_OFFDIS = "Offset Distance"
+PDT_DES_OFFANG = "Offset Angle"
+PDT_DES_OFFPER = "Offset Percentage"
+PDT_DES_WORPLANE = "Choose Working Plane"
+PDT_DES_MOVESEL = "Select Move Mode"
+PDT_DES_OPMODE = "Select Operation Mode"
+PDT_DES_ROTMOVAX = "Rotational Axis - Movement Axis"
+PDT_DES_FLIPANG = "Flip Angle 180 degrees"
+PDT_DES_FLIPPER = "Flip Percent to 100 - %"
+PDT_DES_TRIM = "Trim/Extend only Active Vertex, or All"
+PDT_DES_LIBOBS = "Objects in Library"
+PDT_DES_LIBCOLS = "Collections in Library"
+PDT_DES_LIBMATS = "Materials in Library"
+PDT_DES_LIBMODE = "Library Mode"
+PDT_DES_LIBSER = "Enter A Search String (Contained)"
+PDT_DES_OBORDER = "Object Order to Lines"
+PDT_DES_VALIDLET = "Valid 1st letters; C D E G N P S V, Valid 2nd letters: A D I O P"
+PDT_DES_OUTPUT = "Output for Maths Operations"
+PDT_DES_PPLOC = "Location of PivotPoint"
+PDT_DES_PPSCALEFAC = "Scale Factors"
+PDT_DES_PPSIZE = "Pivot Size Factor"
+PDT_DES_PPWIDTH = "Pivot Line Width in Pixels"
+PDT_DES_PPTRANS = "Pivot Point Transparency"
+PDT_DES_PIVOTDIS = "Input Distance to Compare with Sytem Distance to set Scales"
+PDT_DES_FILLETRAD = "Fillet Radius"
+PDT_DES_FILLETSEG = "Number of Fillet Segments"
+PDT_DES_FILLETPROF = "Fillet Profile"
+PDT_DES_FILLETVERTS = "Use Vertices, or Edges, Set to False for Extruded Geometry"
+PDT_DES_FILLINT = "Intersect & Fillet Two Selected Edges"