可以通过表达式迭代字典中的每个键值对
for k,v in students.items():
由于每个项目的值成分本身就是嵌套Python字典中的字典,因此每个子字典的长度为len(v)。在循环上执行累加,以获得所有元素的计数
>>> students={"student1":{"name":"Raaj", "age":23, "subjects":["Phy", "Che", "maths"],"GPA":8.5},"student2":{"name":"Kiran", "age":21, "subjects":["Phy", "Che", "bio"],"GPA":8.25}} >>> s=0 >>> for k,v in students.items(): s=s+len(v)
>>> s 8
上面的更紧凑的表示将是-
>>> sum(len(v)for v in students.values()) 8