tuple

1. 不可变, iterable

name_tuple = ('bob', 'sam')
for name in name_list:
	print(name)
name_tuple[0] = 'Tim' # error

2. 拆包

user_tuple = ("bobby", 29, 175)
name, age, height = user_tuple
else:
name = user_tuple[0]
age = user_tuple[1]
height = user_tuple[2]
user_tuple = ("bobby", 29, 165, "beijing")
name, *others = user_tuple
print(name, others)
ohters is a list

3. tuple的不可变不是绝对的

name_tuple = ("bobby", [29, 175])
name_tuple[1].append(22)
print(name_tuple)

tuple内的不可hash对象是可变的 4. tuple比list多的功能

1. immutable的重要性

   性能优化

   指出元素全部为immutabble的tuple会作为常量在编译时确定，因此产生了显著的速度差异

   线程安全

   可以作为dict的key

   ··· name_tuple = ('bobby',29） user_info_dict = {} user_info_dict[user_tuple] = "bobby" ···

   拆包特性

2. 如果拿C语言类比，tuple是struct, list是array

namedtuple

1. usage

from collections import namedtuple
User = namedtuple("User", ["name", "age", "height"])
user = User(name="bobby", age=29, height=175)
print(user.age, user.name, user.height)

class User:
	def __init__(self, name, age, height):
		pass
# why not define a class
# namedtuple是tuple的一个子类，使用起来比较简单
# 省空间, 不必创建不需要的类属性
···
2. 可由tuple初始化namedtuple
···
from collections import namedtuple
User = namedtuple("User", ["name", "age", "height"])
user_tuple = ("bobby", 29, 175)
user = User(*user_tuple)
User2 = namedtuple("User", ["name", "age", "height", "edu"])
user2 = User2(*user_tuple, "master")
···
3. _make()的用法

def _make(cls, iterable, ...)

User = namedtuple("User", ['name', 'age', 'height', 'edu']) user_list = ['bobby', 28, 175, 'master'] user_tuple = ('bobby', 28, 175, 'master') user_dict = { "name": "bobby", "age": 29, "height": 175, "edu": "master"} user = User._make(user_list) user2 = User._make(user_tuple) user3 = User._make(user_dict)

4. asdict()的用法 tuple -> dict

def _asdict(self)

User = namedtuple("User", ["name", "age", "height"]) user_tuple = ("bobby", 29, 175) user = User(*user_tuple) user_info_dict = user._asdict()

defaultdict

1. dict usage: setup a dict

users = ['bobby1', 'bobby2', 'bobby3', 'bobby1', 'bobby2', 'bobby1']
duer_dict = {}
for user in users:
	if user not in user_dict:
		user_dict[user] = 1
	else:
		user_dict[user] += 1
print(user_dict)

2. setdefault usage

users = ['bobby1', 'bobby2', 'bobby3', 'bobby1', 'bobby2', 'bobby1']
duer_dict = {}
for user in users:
	user_dict.setdefault(user, 0)
	user_dict[user] += 1
print(user_dict)

3. defaultdict usage

from collections import defaultdict
default_dict = defaultdict(list) # callable object
default_dict['bobby']
users = ['bobby1', 'bobby2', 'bobby3', 'bobby1', 'bobby2', 'bobby1']
default_dict2 = defaultdict(int)
for user in users:
	default_dict2[user] = 1

4. defaultdict and dict

def gen_default():
	return {
		"name": "test",
		"nums": 0
	}

default_dict = defaultdict(gen_default)
default_dict['group1']

# deque
1. usage

from collections import deque example = deque() user_deque = deque(['bobby1', 'bobby2']) user_deque.append('bobby3') user_deque.appendleft('bobby0') user_deque2 = user_deque.copy() # shallow copy print(id(user_deque), di(user_deque2)) import copy user_deque3 = copy.deepcopy(user_deque)

2. deque thread safe/ list is not thread safe
	deque GIL
3. reverse

# Counter