ArcPy SearchCursor getValue leads to NoneType object has no attribute lstrip?

I am having a little bit of a dilemma. I am having a problem with using getValue() and striping the value that is returned. For instance, take the following code.

import arcpy as ap
mxd = ap.mapping.MapDocument("CURRENT")
mylayer = ap.mapping.ListLayers(mxd, "Structures")[0].name

    for row in ap.SearchCursor(mylayer):

        str =  row.getValue("Struct_ID")
        newstr = str1.lstrip('0')

    if str == "662":
        print(str.lstrip('0'))

The error I get no matter what is:

Traceback (most recent call last):
File “”, line 9, in
AttributeError: ‘NoneType’ object has no attribute ‘lstrip’

The code works fine if you take out the newstr = str1.lstrip(’0′) line. The print(str.lstrip(’0′)) statement works fine. I just cannot use str.lstrip anywhere else in the code other then inside of print.

Anyone know what I am doing wrong or is it something to do with Esri?