> bool(0)
False
> bool(1)
True
> bool(-1)
True
> bool(21334)
True

> bool('')
False
> bool(None)
False
> bool('asd')
True
> bool('hello')
True

> a = []
> bool(a)
False
> a.append(1)
> bool(a)
True

> x = raw_input('Please enter a number :')
Please enter a number :
> bool(x.strip())
False
> x = raw_input('Please enter a number :')
Please enter a number :4
> bool(x.strip())
True