python之路——字典

字典 dictionary

字典是python中唯一的映射类型,采用键值对(key-value)的形式存储数据。

1. 可变和不可变

1)可变数据类型:int, str, bool, tuple

2)可变数据类型:list, dict, set

3)字典的 key(键)value

3) key 是唯一的且是不可变的的数据类型。

4) value 是任意数据类型。3.5版本之前字典是无序的,3.6版本之后是有序的。

  

 字典的 增,删,改,查:

1. 字典的增:

 1). 有 key 就有覆盖,没有 key 就添加

#dic = {"name":"jin","age":18,"sex":"male"}
#dic['name2'] = '依米'
#print(dic)

# dic['name'] = '王子'
# print(dic)

#dic['kye'] = value

2). # setdeafult 在字典中添加键值对 (有 key 不变,没有 key 才添加)

dic = {"name":"jin","age":18,"sex":"male"}
# dic.setdefault('hobby')
# print(dic) # {'name': 'jin', 'age': 18, 'sex': 'male', 'hobby': None}

# dic.setdefault('hobby','开车')
# print(dic)  # {'name': 'jin', 'age': 18, 'sex': 'male', 'hobby': '开车'}

# dic.setdefault('name','taibai')
# print(dic)
View Code

2.  字典的删:

1). pop 按 key (键)删除,有返回值,并且如果没有此 key , 可设置返回值。

dic = {"name":"jin","age":18,"sex":"male"}
# ret = dic.pop('sex')
# print(ret)

# ret = dic.pop('sex1','没有此键')
# print(ret)

2). clear (清空)

dic = {"name":"jin","age":18,"sex":"male"}

# dic.clear()
# print(dic)

3). del 删除字典,删除键值对

dic = {"name":"jin","age":18,"sex":"male"}

# del dic['name']
# print(dic)

#del dic['age']
#print(dic)

4). popitem () 随机删除

dic = {"name":"jin","age":18,"sex":"male"}

# reb = dic.popitem()
# print(reb)
# print(dic)

3. 字典的改:dic['key'] = value,有 key 就覆盖。

# update (更新,更改,校正):将dic 的键值对,覆盖,添加dic2中,dic不变。

dic = {"name":"jin","age":18,"sex":"male"}
#dic2 = {'name':"alex",'weight':74}
#dic2.update(dic)
#print(dic)
#print(dic2)

4). 字典的查:

dic = {"name":"jin","age":18,"sex":"male"}

#print(dic['name'])
# print(dic.get('name'))
# print(dic.get('name2','没有此键值对'))

3. 字典的键 (key),值(value),键值对 (item):

dic = {"name":"jin","age":18,"sex":"male"}
#keys = dic.keys()
#print(keys,type(leys))

# k = list(keys)
# print(k,type(k))

# values = dic.values()
# print(values)

# items = dic.items()
# print(items)

# for k,v in dic.items():
# print(k,v)
 

4. 字典的嵌套:

dic = {
'name':'金鑫',
'name_list':[1,2,3,'李杰'],
1:{
'python10':['小黑','萌哥'],
'老男孩':{'name':'oldboy','age':56}
}
}
#1,[1,2,3,'李杰']追加'wusir'
dic['name_list'].append('wusir')
print(dic)
#
#2, ['小黑','萌哥'] 小黑 萌哥中间 插入一个花哥
l = dic[1]['python10']
l.insert(1,'花哥')
print(dic)
#
#3, {'name':'oldboy','age':56} 添加一个键值对,hobby:男人
dic1 = dic[1]
dic2 = dic1['老男孩']
dic2['hobby'] = '男人难'
print(dic)

dic['name'] = '王子'
print(dic)

dic.setdefault('hobby')
print(dic)
View Code

 

 

 

 

 

posted @ 2018-01-25 18:13  lzg世界  阅读(100)  评论(0编辑  收藏  举报
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