Sys module

[Uchikago]

can any body explain why this didn't work

#test1.py
var=99
def glob3():
    var=0
    import sys
    glob=sys.modules['test1']
    glob.var+=1
glob3()
print(var)      #python report an error

But when i import that test1 module in interactive prompt, it worked:

>>> import test1
100