Python文件操作,时间日期操作,collections增强,Deque(类似java的LinkedList),OrderedDict,Counter

1、文件操作的案例:

#文件操作的三种方式
#r = read 读取文件
#w = write 写入文件,覆盖掉
#a = append 追加写入,不会覆盖原有的内容
#读文件
f = open("E://wordcount//input//1.txt","r")
data = f.read()
print(data)

#读文件 一行一行的读取
path = "E://wordcount//input//1.txt"
f = open(path,"r")
for line in f.readlines():
    print("------------->" + line)

##覆盖写
path = "E://wordcount//input//1.txt"
f = open(path,"w",encoding="utf-8")
##这种方式写的时候,会吧别人的覆盖了。
f.write("I love my country")
f.close()

##追加写
path = "E://wordcount//input//2.txt"
f = open(path,"a",encoding="utf-8")
#写一个分割
f.write("\n")
f.write("I love you two")
f.close()

#python中的try,catch
#异常处理的格式
try:
    path = "E://wordcount//input//2.txt"
    f = open(path,"r",encoding="utf-8")
    for line in f.readlines():
        print(line)
finally:
    #不管怎样都关闭掉文件
    f.close()

##异常处理的简单写法
with open(path,"r",encoding="utf-8") as f:
    for i in f.readlines():
        print("xxxx" + i)

2、Python中的操作时间

将date类型转化成固定的字符串
将字符串转化成date类型

#将date转换成字符串

#使用datetime需要导入一个类库,下面是导入类型对的方式,导包的方式还是选中
#datetime,然后Alt + Enter键,选择合适的包
from datetime import datetime,timedelta
#获取当前时间
now = datetime.now()
print(now)

#将事件转成成有格式类型的时间
str_time = now.strftime("%Y-%m-%d %H:%M:%S")
print(str_time)

##将字符串转为Date类型
date = datetime.strptime("20170714 19:27:51","%Y%m%d %H:%M:%S")
print(date)

#对日期进行修改
now = datetime.now()
#在现有的基础上加8个小时
now = now + timedelta(hours=8)
print(now)

##加3天
now = now + timedelta(days=3)
print(now)

#减3天
now = now + timedelta(days=-3)
print(now)
#减8小时
now = now + timedelta(hours=-8)
print(now)

运行结果:
Python文件操作,时间日期操作,collections增强,Deque(类似java的LinkedList),OrderedDict,Counter_第1张图片

3.collections增强

namedtuple:能够tuple的每个元素起个名字
基于tuple的扩展,tuple一旦被创建无法修改,获取tuple中的数据,只能通过角标值进行修改。

from collections import namedtuple

tuple = ("name","age","sex")
#通过角标值获取元素
tuple[0]

#namedtuple,如果作为一个单独的数据结构,就是每个元素都有名称
#并且一旦创建,就无法修改。
Point = namedtuple("Point",["name","age","sex"])
p = Point("旺财","3","公")
print(p.name)

运行结果:
Python文件操作,时间日期操作,collections增强,Deque(类似java的LinkedList),OrderedDict,Counter_第2张图片

Deque:
相当于java中的linkedlist,特征:查询慢,删除修改快。

from collections import deque

#linked的定义
linked_list = deque(["1","2","3","4"])
#获取linkedlist的元素 和删除元素
item = linked_list.pop()
print(linked_list)
item = linked_list.popleft()
print(item)
print(linked_list)
#添加元素,append默认在最后面添加4,appendLeft默认在最左边添加元素
linked_list.append("4")
linked_list.appendleft("1")
print(linked_list)

运行结果:

deque(['1', '2', '3'])
1
deque(['2', '3'])
deque(['1', '2', '3', '4'])

4 OrderedDict

from collections import OrderedDict
#orderdict 按照插入的顺序排序
map = OrderedDict([("key1",3),("key2",2),("key0",1)])
for item in map.items():
    print(item)

运行结果:

('key1', 3)
('key2', 2)
('key0', 1)
from collections import Counter
#计数器,计算每个字符出现的次数
#单词计算
counter = Counter()
str = "dasetgerfa"
for ch in str:
    counter[ch] = counter[ch] + 1
print(counter)

运行结果是:

Counter({'a': 2, 'e': 2, 'd': 1, 's': 1, 't': 1, 'g': 1, 'r': 1, 'f': 1})

上面实现的逻辑相当于是:

map = dict()
str = "hello"
for ch in str:
    value = map.get(ch)
    if value == None:
        map[ch] = 1
    else:
        value += 1
        map[ch] = value
print(map)

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