8.3 内置函数

Python包含了以下内置函数

len

>>> len("hello python")
12
>>> len([1, 2, 3, 4])
4
>>> len((3,4))
2
>>> len({"a":1, "b":2})
2

注意：len在操作字典数据时，返回的是键值对个数。

max

>>> max("hello python")
'y'
>>> max([1,4,522,3,4])
522
>>> max({"a":1, "b":2})
'b'
>>> max({"a":10, "b":2})
'b'
>>> max({"c":10, "b":2})
'c'

del

del有两种用法，一种是del加空格，另一种是del()

>>> a = 1
>>> a
1
>>> del a
>>> a
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'a' is not defined
>>> a = ['a', 'b']
>>> del a[0]
>>> a
['b']
>>> del(a)
>>> a
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'a' is not defined

多维列表/元祖访问的示例

>>> tuple1 = [(2,3),(4,5)]
>>> tuple1[0]
(2, 3)
>>> tuple1[0][0]
2
>>> tuple1[0][2]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: tuple index out of range


>>> tuple1[0][1]
3
>>> tuple1[2][2]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: list index out of range


>>> tuple2 = tuple1+[(3)]
>>> tuple2
[(2, 3), (4, 5), 3]
>>> tuple2[2]
3
>>> tuple2[2][0]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'int' object is not subscriptable