How can i select by number of vertices? I have the latest version of blender and i downloaded a script called mesh_face_info_select.py which lets me select all tris quads or ngons of the mesh but i get an error when i use the script where the operator bpy.ops.mesh.select_by_number_vertices is not found. I assume that it was removed from blender? I have searched in google but didn't find anything.
Sounds like the script you downloaded has a bug or is used differently.
You can try contacting the author and describe the error, s/he might fix it.

Anyway, you can paste this to your text editor, change the value of vertCount and press "Run script", it will select all the faces with the number of verts specified in the vertCount variable.

import bpy, bmesh

vertCount = 3 # &lt;-- Faces with this amount of verts will be selected

bpy.ops.object.mode_set( mode = 'EDIT' )
bm = bmesh.from_edit_mesh( bpy.context.object.data )

bpy.ops.mesh.select_mode( type = 'FACE' )
bpy.ops.mesh.select_all( action = 'DESELECT' )

for f in bm.faces: 
    if len( f.verts ) == vertCount: 
        f.select = True

bm.select_flush(True)