python day04 字符串、列表、元组

day04 字符串、列表、元组

复习

1、字符串

• 需要掌握

  1. strip,lstrip,rstrip

     msg = '****hello*****'
     msg.strip('*') >>>> hello
     msg.lstrip('*') >>>> hello*****
     msg.rstrip('*') >>>> ****hello
     

  2. upper,lower

  3. startwith,endwith

  4. format的三种用法

     'my name is {x} my age is {y}'.format(y=18,x='hina')
     'my name is {} my age is {}'.format(18,'hina')
     'my name is {1} my age is {0}{1}{1}{0}'.format(18,'hina')
     

5. split,rsplit

   msg = 'a:b:c:d'
   msg.split(":",1)>>>>>['a','b:c:d']
   msg.rsplit(":",1)>>>>>['a,b,c','d']
   

6. join

   ':'.join(['aa','bb','cc'])
   >>>>'aa:bb:cc'
   

7. replace

   msg = 'hello world'
   msg.replace('l','m')
   >>>>hemmo wormd
   msg.replace('l','m',1)
   >>>>hemlo w	orld
   

8. isdigit

   msg = '123'
   msg.isdigit()
   >>>>True
   

• 需要了解

  # 需要了解的方法
  #1、find,rfind,index,rindex,count
  # msg = "hello egon xxx egon yyy egon zzz"
  # print(msg.find("egon",0,7))
  # print(msg.index("egon"))
  # print(msg.rfind("egon"))
  # print(msg.rindex("egon"))
  
  # print(msg.find("abcde"))
  # print(msg.index("abcde"))
  
  # print(msg.count("egon"))
  
  #2、center,ljust,rjust,zfill
  # print('egon'.center(50,'*'))
  # print('egon'.ljust(50,'*'))
  # print('egon'.rjust(50,'*'))
  # print('egon'.zfill(50))
  # print('egon'.rjust(50,"0"))
  
  #3、captalize,swapcase,title
  msg = "hellO woRld"
  # print(msg.capitalize())
  
  # print(msg.swapcase())
  # print(msg.title())
  
  #4、is数字系列
  
  #5、is其他
  # name='egon123'
  # print(name.isalnum()) #字符串由字母或数字组成
  # print(name.isalpha()) #字符串只由字母组成
  #
  # print(name.islower())
  # print(name.isupper())
  
  # name="     "
  # print(name.isspace())
  
  # name ="Hello World"
  # print(name.istitle())
  
  n1 = b'4'
  n2 = '4'
  n3 = '四'
  n4 = 'Ⅳ'
  
  print(n1.isdigit())>>>>True
  print(n2.isdigit())>>>>True
  print(n3.isdigit())>>>>False
  print(n4.isdigit())>>>>False
  
  print(n2.isnumeric())>>>True
  print(n3.isnumeric())>>>True
  print(n4.isnumeric())>>>True
  

2、列表类型

1. 用途：按位置存储多个值

2. 定义方式：在[ ]内用，分割开任意类型元素

   所有可以被for循环遍历的类型都可以传给list转化为列表
   list({'k1':11,'k2':22})
   >>>['k1','k2']
   

3. 常用操作和内置方法

   list = [111,222,333,444,555]
   print(id(list))
   list[0]=666
   print(id(list))
   print(list)
   
   # 列表不可以根据不存在的索引赋值
   list[7]=777>>>>IndexError:下标超出范围
       
   # 追加
   list.append(666)
   
   # 插入
   list.insert(0,666)>>>>[666,111,222,333,444,555]
   
   # 切片
   l = [11,22,33,44]
   l1 = l[:]  # 浅拷贝
   
   # 长度
   len(l)
   
   # 成员运算
   in/ not in
   
   # 删除
   l = [11, 22, 33]
   del l[0]
   print(l)
   >>>>[22, 33]
   
   l = [11, 22, 33]
   l.remove(11)
   print(l)
   >>>>
   [22, 33]
   
   l = [11, 22, 33]
   res = l.pop(0)
   print(l)
   print(res)
   >>>>
   [22, 33]
   11
   
   l = [11, 22, 33]
   l.reverse()
   print(l)
   >>>>
   [33, 22, 11]
   
   # 清空l还存在====l=[]
   l.clear 
   
   l = [11, 22, 33]
   l1 = [44, 55, 66]
   l.extend(l1)
   print(l)
   >>>>
   [11, 22, 33, 44, 55, 66]
   
   l.index(33,0,1)
   >>>>ValueError
   
   l = ['44', '11', '22', '33', 'x']
   l.sort()
   print(l)
   >>>>
   ['11', '22', '33', '44', 'x']
   l.sort(reverse=True)
   >>>>
   ['x', '44', '33', '22', '11']
   

队列：先进先出

堆栈：后进先出

3、元组类型

1. 用途

2. 定义方式：在()内用逗号分隔开多个任意类型的元素

   x = (10,)  # x = tuple(...)
   # tuple可以把任意能够被for循环遍历的类型转化为元组
   

3. 元组的常用操作+内置方法

   t = (11,22,33,44)
   # 1.索引
   print(t[0])
   # 2.切片
   t[0:3]
   # 3.长度
   len(t)
   # 4.成员运算 in 和 not in
   # 5.循环
   

总结：存多个值，有序，不可变

列表存的是索引与对应值得内存地址的绑定关系

t = (111,222,333,[444,555])
t[-1][0]=666
print(t)
>>>>
(111,222,333,[666,555])

l = [111, 222, 333]
print(id(l))
l[0] = 444
print(id(l))
print(l)
>>>>
2310692163328
2310692163328
[444, 222, 333]

t = (111, 222, 333, [44, 555])
print(id(t[0]), id(t[1]), id(t[2]), id(t[3]))
t[-1][0] = 666
print(id(t[0]), id(t[1]), id(t[2]), id(t[3]))
print(t)
>>>>
2626267207472 2626267211088 2626275091888 2626275397248
2626267207472 2626267211088 2626275091888 2626275397248
(111, 222, 333, [666, 555])

4、字典类型

1. 用途

2. 定义方式：在{}内用逗号分隔多个元素，每个元素都是key:value的格式，其中value可以是任意类型，而key必须是不可变类型，通常是str类型，而且key不能重复

   dict数据类型转换

   info = [('k1',111),('k2',222),('k3',333)]
   dic = dict(info)
   print(dic)
   >>>>
   {'k1': 111, 'k2': 222, 'k3': 333}
   
   print(dict(x=1,y=2,z=3))
   >>>>
   {'x': 1, 'y': 2, 'z': 3}
   

3. 长度：len(dict)

4. 成员运算 in 和 not in： 以key为主

5. 删除

   dic = {'name':'hina','age':18}
   # 单纯的删除
   del dic['name']
   print(dic)
   # 取走
   v = dic.pop('name')
   print(v)
   print(dic)
   >>>>
   hina
   {'age': 18}
   
   dic = {'name':'hina','age':18}
   v = dic.popitem()
   print(v)
   >>>>
   ('age', 18)
   

6. keys，values，items

   dic = {'name':'hina','age':18}
   print(dic.keys())
   print(dic.values())
   for k,v in dic.items():
       print(k,v)
   >>>>
   dict_keys(['name', 'age'])
   dict_values(['hina', 18])
   name hina
   age 18
   

7. get：dic.get('key')与dic['key']相似，不同点在于若dic中没有key则dic['key']会报错

8. 其他

   dic = {'name':'hina','age':18}
   dic.update({'gender':'male',"age":20})
   print(dic)
   >>>>
   {'name': 'hina', 'age': 20, 'gender': 'male'}
   
   print({}.fromkeys(['name', 'age', 'gender'],None))
   >>>>
   {'name': None, 'age': None, 'gender': None}
   
   v = dic.setdefault('name','xxx') # 等价于下面的代码，返回值为dic中name对应的值
   if 'name' not in dic:
       dic['name'] = 'xxx'
   

总结：存多个值，可变，字典本身不可变

for i in enumerate([1,2,3,4,5,'xxx','yyy']):
    print(i)
>>>>
(0, 1)
(1, 2)
(2, 3)
(3, 4)
(4, 5)
(5, 'xxx')
(6, 'yyy')

for j in zip(['a','b','c','d'],('A','B','C','D','E')):
    print(j)
>>>>
('a', 'A')
('b', 'B')
('c', 'C')
('d', 'D')