python之数据类型3和文件操作
一 字典属性方法补充
key是不变的类型,字典能快速查找,基于哈希索引
不可变类型 int bool str tuple 可变类型:list dict set
1 clear :清空
# d={
# 'k1':'v1',
# 'k2':'v2'
# }
# d.clear()
# print(d) #清空
2 Cory:拷贝
# d={
# 'k1':'v1',
# 'k2':'v2'
# }
# a=d.copy()
# print(a) #拷贝
3 fromkeys:生成一个字典,类下面的一个属性方法
a=dict.fromkeys(['k1','k2','k3'],[1,2])
print(a)
4 pop :删除
# d={
# 'k1':'v1',
# 'k2':'v2'
# }
# d.pop('k1')
# print(d) #按照key删除
5 popitem : 删除整个元素
# d={
# 'k1':'v1',
# 'k2':'v2'
# }
# d.popitem()
# print(d) #删除整个键值对
6 setdefault:只添加不修改
# d={
# 'k1':'v1',
# 'k2':'v2'
# }
# d.setdefault('k3','v3')
# print(d) #添加元素
7 update :存在的话跟新,没有就会添加
# d={
# 'k1':'v1',
# 'k2':'v2'
# }
# d.update({'k2':'v3','k3':'v2'})
# print(d) #添加,如果key存在,修改value值
二 集合以及集合的功能
集合内的元素是唯一的,集合内的元素必须是可hash的,也就是可变类型。集合是无序的
1 add :添加不可能重复
# a={'fang','jie','lei','dong','tao'}
# a.add('qq') #添加,如果集合里面有,就不会添加
# print(a)
2 clear :清空
# a={'fang','jie','lei','dong','tao'}
# a.clear() #清空
# print(a)
3 copy :拷贝
# a={'fang','jie','lei','dong','tao'}
# b=a.copy() #拷贝
# print(b)
4 difference :差集只存在一个集合的
# a={'fang','jie','lei','dong','tao'}
# b={'fang','rei','cheng'}
# print(a - b) #差集 # a={'fang','jie','lei','dong','tao'}
# b={'fang','rei','cheng'}
# print(a.difference(b)) #查看差集
5 difference_update:找差集并更新
# a={'fang','jie','lei','dong','tao'}
# b={'fang','rei','cheng'}
# a.difference_update(b)
# print(a) #查找差集并更新
6 symmetric_difference :找对称差集
# a={'fang','jie','lei','dong','tao'}
# b={'fang','rei','cheng'}
# print(a ^ b) #对称差集
#
# a={'fang','jie','lei','dong','tao'}
# b={'fang','rei','cheng'}
# print(a.symmetric_difference(b)) #查看对称差集
7 symmetric_difference_update: 着对称差集并更新
# a={'fang','jie','lei','dong','tao'}
# b={'fang','rei','cheng'}
# a.symmetric_difference_update(b)
# print(a) #查找对称差集并更新
8 discard :根据对象删除
# a={'fang','jie','lei','dong','tao'}
# b={'fang','rei','cheng'}
# a.discard('jie')
# print(a) #删除
9 intersection:交集
# a={'fang','jie','lei','dong','tao'}
# b={'fang','rei','cheng'}
# print(a & b) #交集 # a={'fang','jie','lei','dong','tao'}
# b={'fang','rei','cheng'}
# print(a.intersection(b)) #交集
10 intersection_update:交集并更新
# a={'fang','jie','lei','dong','tao'}
# b={'fang','rei','cheng'}
# a.intersection_update(b)
# print(a) #查找并集并更新
11 union :并集
# a={'fang','jie','lei','dong','tao'}
# b={'fang','rei','cheng'}
# print(a | b) #并集
#
# a={'fang','jie','lei','dong','tao'}
# b={'fang','rei','cheng'}
# print(a.union(b)) #并集
12 isdisjoint :判断是否无交集
# a={'fang','jie','lei','dong','tao'}
# b={'fang','rei','cheng'}
# print(a.isdisjoint(b)) #判断是否无交集
13 iscubset :判断是否是子集
# a={'fang','jie','lei','dong','tao'}
# b={'fang','jie'}
# print(b.issubset(a)) #判断b是不是a的子集
14 issuperset :判断是否是父集
# a={'fang','jie','lei','dong','tao'}
# b={'fang','jie'}
# print(a.issuperset(b)) #判断a是不是b的父集
15 pop 随机删除
# a={'fang','jie','lei','dong','tao'}
# a.pop()
# print(a) #随机删除
16 remove :指定删除
# a={'fang','jie','lei','dong','tao'}
# a.remove('fang')
# print(a) #指定元素删除
17 update :更新
# a={'fang','jie','lei','dong','tao'}
# b={'fang','rei','cheng'}
# a.update()
# print(a) #更新
18 len :长度
# a={'fang','jie','lei','dong','tao'}
# print(len(a))
set一般的情况下,集合属性前面必须放集合,属性后面可以放任意的数据类型,集合里面的值是不可以变得。{}默认是字典,想要创建集合就是set()
三 文件操作
文件的常用方法右
1,r(read):读取文件,只能读取,不能其他操作; r+:不光是可以读取,而且还可以写入,r+是先读取再写入
2 ,w(write):写入文件,只能写入; w+:不过可以写入,而且还可以写入过后再去读取。
3 ,a(append):追加内容,只能追加; a+:追加过后还可以读取文件
# #以bytes类型写入文件
# a=b'\xe4\xbd\xa0\xe4\xb8\xaa\xe5\xa4\xa7\xe5\x82\xbb\xe5\x8f\x89\r\n\xe9\x82\xa3\xe4\xba\xba\xe5\xb0\xb1\xe6\x98\xaf\xe4\xbd\xa0'
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','wb')
# b=f.write(a)
# f.close()
#
# #以w覆盖的方式写入
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','w',encoding='utf-8')
# b=f.write('dsdf')
# f.close() #
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','w+',encoding='utf-8')
# f.write('dsdfdfsd')
# f.seek(0) #seek()指定光标的位置
# a=f.read()
# f.close()
# print(a) # a#追加的方式添加
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','a',encoding='utf-8')
# b=f.write('dsdf')
# f.close() ##追加过后再读取
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','a+',encoding='utf-8')
# b=f.write('dsdf')
# f.seek(0)
# a=f.read()
# f.close()
# print(a) # #以bytes类型读取
# f=open('E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt',mode='rb')
# a=f.read()
# f.close()
# print(a)
#
# #以utf-8格式读取
# f=open('E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt',mode='r',encoding='utf-8')
# a=f.read()
# f.close()
# print(a) ##先读取在追加
# f=open('E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt',mode='r+',encoding='utf-8')
# a=f.read()
# f.seek(3)
# f.write('jie')
# f.close()
# print(a)
#
文件下的属性操作:
1 read:读取文件
# with open('E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','r',encoding='utf-8')as f :
# obj=f.read()
# print(obj)
2 write:写入文件
#格式2 :
# with open('E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','w',encoding='utf-8')as f :
# f.write('yi')
3 seek:调整光标的位置
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','w+',encoding='utf-8')
# f.write('dsdfdfsd')
# f.seek(0) #seek()指定光标的位置
# a=f.read()
# f.close()
# print(a)
4 tell:读取光标的位置
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','w+',encoding='utf-8')
# f.write('dsdfdfsd\nfsd\nfgs')
# a=f.tell() #查找光标的位置
# print(a)
5 writable:是否可写
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','w+',encoding='utf-8')
# a=f.writable() #判断是否可写
# print(a)
6 readable:是否可读
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','w+',encoding='utf-8')
# f.write('dsdfdfsd\nfsd\nfgs')
# f.seek(0)
# a=f.readable() #判断是否可读
# f.close()
# print(a)
7 close:关闭文件
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','w+',encoding='utf-8')
# f.write('dsdfdfsd\nfsd\nfgs\ndas')
# f.close() #关闭
8 flush:刷到硬盘
# f=open('E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt',mode='r+',encoding='utf-8')
# a=f.read()
# f.seek(3)
# f.flush() #flush 刷到硬盘
# f.write('jie')
# f.close()
# print(a)
9 fileno:文件对象
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','w+',encoding='utf-8')
# f.write('dsdfdfsd\nfsd\nfgs\ndas')
# a=f.fileno() #文件对象
# f.close()
# print(a)
10 isatty :判断是否输出设备
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','w+',encoding='utf-8')
# f.write('dsdfdfsd\nfsd\nfgs')
# f.seek(0)
# a=f.isatty() #判断是否是输出设备
# f.close()
# print(a)
11 readline:读取一行内容
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','w+',encoding='utf-8')
# f.write('dsdfdfsd\nfsd\nfgs')
# f.seek(0)
# a=f.readline() #只读取整行
# f.close()
# print(a)
12 seekable:判断是否可设置指针
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','w+',encoding='utf-8')
# f.write('dsdfdfsd\nfsd\nfgs')
# a=f.seekable() #判断是否可设置指针
# print(a)
13 truncate : 光标后面的内容不要了,只要光标前面的内容
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','w+',encoding='utf-8')
# f.write('dsdfdfsd\nfsd\nfgs\ndas')
# f.truncate(5) #指定光标的位置,然后再保留光标前面的内容是删除光标后面的内容
# f.close()
14 readlines:读取所有的内容,然后一块督导内存
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','w+',encoding='utf-8')
# f.write('dsdfdfsd\nfsd\nfgs')
# f.seek(0)
# a=f.readlines() #全部读取,返回是列表,元素字符串
# f.close()
# print(a)
python2 中的xreadlines就相当于python3中的for line in f:
# f=open(r'E:\pycharm\pycharm\PyCharm Community Edition 2017.1.3\day7\jie.txt','w+',encoding='utf-8')
# f.write('dsdfdfsd\nfsd\nfgs')
# f.seek(0)
# for line in f:
# print(line)
# f.close()
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