Dictionary
创建词典
python
# {} 或 dict() 内置函数来创建空字典
empty_dict = {} # 输出: {}
empty_dict2 = dict() # 输出: {}
# Dictionary with data values
dct = {'key1':'value1', 'key2':'value2', 'key3':'value3', 'key4':'value4'}
# 值可以是任何数据类型：字符串，布尔值，列表，元组，集合或字典
person = {
'first_name':'he',
'last_name':'fang',
'age':20,
'country':'Finland',
'is_marred':Flase,
'skills':['JavaScript', 'React', 'Node', 'MongoDB', 'Python'],
'address':{
'street':'Space street',
'zipcode':'02210'
}
}词典长度
python
dct = {'key1':'value1', 'key2':'value2', 'key3':'value3', 'key4':'value4'}
print(len(dct)) # 4
person = {
'first_name':'he',
'last_name':'fang',
'age':20,
'country':'Finland',
'is_marred':Flase,
'skills':['JavaScript', 'React', 'Node', 'MongoDB', 'Python'],
'address':{
'street':'Space street',
'zipcode':'02210'
}
}
print(len(person)) # 7访问字典项
python
# 通过引用它的键名来访问字典项
dct = {'key1':'value1', 'key2':'value2', 'key3':'value3', 'key4':'value4'}
print(dct['key1']) # value1
print(dct['key4']) # value4
person = {
'first_name':'he',
'last_name':'fang',
'age':20,
'country':'Finland',
'is_marred':Flase,
'skills':['JavaScript', 'React', 'Node', 'MongoDB', 'Python'],
'address':{
'street':'Space street',
'zipcode':'02210'
}
}
print(person['first_name']) # he
print(person['country']) # Finland
print(person['skills']) # ['JavaScript', 'React', 'Node', 'MongoDB', 'Python']
print(person['skills'][0]) # JavaScript
print(person['address']['street']) # Space street
print(person['city']) # Error将项目添加到字典
python
# 我们可以向字典中添加新的键值对
dct = {'key1':'value1', 'key2':'value2', 'key3':'value3', 'key4':'value4'}
dct['key5'] = 'value5'
person = {
'first_name':'he',
'last_name':'fang',
'age':20,
'country':'Finland',
'is_marred':Flase,
'skills':['JavaScript', 'React', 'Node', 'MongoDB', 'Python'],
'address':{
'street':'Space street',
'zipcode':'02210'
}
}
person['job_title'] = 'Instructor'
person['skills'].append('HTML')
print(person)修改字典中的项目
python
dct = {'key1':'value1', 'key2':'value2', 'key3':'value3', 'key4':'value4'}
dct['key1'] = 'value-one'
person = {
'first_name':'he',
'last_name':'fang',
'age':20,
'country':'Finland',
'is_marred':Flase,
'skills':['JavaScript', 'React', 'Node', 'MongoDB', 'Python'],
'address':{
'street':'Space street',
'zipcode':'02210'
}
}
person['first_name'] = 'Eyob'
person['age'] = 252检查字典中的键
python
# 我们使用in操作符来检查字典中是否存在键
dct = {'key1':'value1', 'key2':'value2', 'key3':'value3', 'key4':'value4'}
print('key2' in dct) # True
print('key5' in dct) # False
# 使用get方法 检查键是否存在
# 如果键不存在，get方法返回None，这是NoneType对象数据类型
person = {
'first_name':'he',
'last_name':'fang',
'age':20,
'country':'Finland',
'is_marred':Flase,
'skills':['JavaScript', 'React', 'Node', 'MongoDB', 'Python'],
'address':{
'street':'Space street',
'zipcode':'02210'
}
}
print(person.get('first_name')) # he
print(person.get('country')) # Finland
print(person.get('skills')) #['HTML','CSS','JavaScript', 'React', 'Node', 'MongoDB', 'Python']
print(person.get('city')) # None从字典中删除键和值对
python
# pop(key) 删除指定键值的项
# popitem(key) 删除最后一项
# del 删除指定键值的项
dct = {'key1':'value1', 'key2':'value2', 'key3':'value3', 'key4':'value4'}
dct.pop('key1') # removes key1 item
dct = {'key1':'value1', 'key2':'value2', 'key3':'value3', 'key4':'value4'}
dct.popitem() # removes the last item
del dct['key2'] # removes key2 item
person = {
'first_name':'he',
'last_name':'fang',
'age':20,
'country':'Finland',
'is_marred':False,
'skills':['JavaScript', 'React', 'Node', 'MongoDB', 'Python'],
'address':{
'street':'Space street',
'zipcode':'02210'
}
}
person.pop('first_name') # Removes the firstname item
person.popitem() # Removes the address item
del person['is_married'] # Removes the is_married item将字典更改为项目列表
python
# items() 方法将字典更改为元组列表
dct = {'key1':'value1', 'key2':'value2', 'key3':'value3', 'key4':'value4'}
dct1 = dct.items()
print(dct1) # dict_items([('key1', 'value1'), ('key2', 'value2'), ('key3', 'value3'), ('key4', 'value4')])
print(type(dct)) # <class 'dict'>
print(type(dct1)) # <class 'dict_items'>清除字典
python
# clear()
dct = {'key1':'value1', 'key2':'value2', 'key3':'value3', 'key4':'value4'}
print(dct.clear()) # None删除字典
python
# del 完全删除字典
dct = {'key1':'value1', 'key2':'value2', 'key3':'value3', 'key4':'value4'}
del dct复制字典
python
# copy() 复制字典
dct = {'key1':'value1', 'key2':'value2', 'key3':'value3', 'key4':'value4'}
dct_copy = dct.copy() # {'key1':'value1', 'key2':'value2', 'key3':'value3', 'key4':'value4'}以列表的形式获取字典键
python
# keys() 以列表的形式为我们提供了字典的所有键
dct = {'key1':'value1', 'key2':'value2', 'key3':'value3', 'key4':'value4'}
keys = dct.keys()
print(keys) # dict_keys(['key1', 'key2', 'key3', 'key4'])以列表的形式获取字典值
python
# values() 方法将字典中的所有值作为列表提供给我们
dct = {'key1':'value1', 'key2':'value2', 'key3':'value3', 'key4':'value4'}
values = dct.values()
print(values) # dict_values(['value1', 'value2', 'value3', 'value4'])