The pit that Python's Django framework has stepped on (6)

Passing parameter to type error int() at line 37

ValueError at /herolist/
invalid literal for int() with base 10: ''
Request Method: GET
Request URL: http://127.0.0.1:8000/herolist/
Django Version: 1.8.2
Exception Type: ValueError
Exception Value: invalid literal for int() with base 10: '' Exception Location: /home/python/Desktop/django/test5/booktest/views.py in HeroList, line 37 Python Executable: /home/python/.virtualenvs/h1/bin/python Python Version: 2.7.12 Python Path: ['/home/python/Desktop/django/test5',  '/home/python/.virtualenvs/h1/lib/python2.7',







 '/home/python/.virtualenvs/h1/lib/python2.7/plat-x86_64-linux-gnu',
 '/home/python/.virtualenvs/h1/lib/python2.7/lib-tk',
 '/home/python/.virtualenvs/h1/lib/python2.7/lib-old',
 '/home/python/.virtualenvs/h1/lib/python2.7/lib-dynload',
 '/usr/lib/python2.7',
 '/usr/lib/python2.7/plat-x86_64-linux-gnu',
 '/usr/lib/python2.7/lib-tk',
 '/home/python/.virtualenvs/h1/local/lib/python2.7/site-packages',
 '/home/python/.virtualenvs/h1/lib/python2.7/site-packages']
Server time: 星期日, 1 四月 2018 14:49:22 +0800