三. 字典以及相关使用
1. 字典的定义 dict{}
2. 字典特征: 字典是无序的, key-value 键值对形式, key 值不重复
3. 字典的赋值: dictA = {keyA: valueA, keyB: valueB, keyC: valueC}
4. 字典的取值: dictA[keyA] dictA.get(keyA)
5. 字典的所有键: dictA.keys() key-value 获取: dictA.items()
6. 修改字典中元素的值: dictA[keyA] = value
7. 获取字典的长度: len(dictA)
8. 字典中添加元素: dictA[key_new] = value
9. 删除字典所有元素: dictA.clear()
10. 删除整个字典: del dictA
11. 字典组合: dict(dictA, **dictB) dictA.update(dictB)
四. 实例
1. 字典的定义, 字典的键名只能是数字, 字符串, 元组, 且不能重复
stu1 = {"name": "Mr. 逗", "sex": "male", "age": 20, "hobby": "run"}
print(stu1)
结果:
{'sex': 'male', 'hobby': 'run', 'name': 'Mr. 逗', 'age': 20}
2. 字典取值: dictA[keyA] dictA.get(keyA)
stu1 = {"name": "Mr. 逗", "sex": "male", "age": 20, "hobby": "run"}
- print(stu1["name"])
- print(stu1.get("name"))
结果:
Mr. 逗
Mr. 逗
3. 修改字典值: dictA[keyA] = value,keyA 是已存在的 key
stu1 = {"name": "Mr. 逗", "sex": "male", "age": 20, "hobby": "run"}
- stu1["name"] = "Mr. 小小逗"
- print(stu1)
结果:
{'hobby': 'run', 'age': 20, 'name': 'Mr. 小小逗', 'sex': 'male'}
4. 向字典中添加键值对, dictA[key_new] = value,key_new 是不存在的
stu1 = {"name": "Mr. 逗", "sex": "male", "age": 20, "hobby": "run"}
stu1["study"] = "python"
结果:
{'age': 20, 'study': 'python', 'name': 'Mr. 逗', 'sex': 'male', 'hobby': 'run'}
5. 获取字典的长度: len(dictA)
stu1 = {"name": "Mr. 逗", "sex": "male", "age": 20, "hobby": "run"}
print(len(stu1))
结果:
4
6. 两个字典的组合: dictA.update(dictB) dict(dictA, **dictB)
- B = {"name": "xiaojian", "age": 28, "is_marry": False}
- B.update({"role": "teacher", "class": "python"})
- print(B)
结果:
{'class': 'python', 'is_marry': False, 'age': 28, 'role': 'teacher', 'name': 'xiaojian'}
- B = {"name": "xiaojian", "age": 28, "is_marry": False}
- C = {"role": "teacher", "class": "python"}
- D = dict(B, **C)
- print(D)
结果:
{'class': 'python', 'is_marry': False, 'age': 28, 'role': 'teacher', 'name': 'xiaojian'}
7. 删除字典中所有元素: dictA.clear(), 只是清空字典
- a = {"name": "Jack", "sex": "M"}
- a.clear()
- print(a)
结果:
{}
8. 删除整个字典: del dictA
- a = {"name": "Jack", "sex": "M"}
- del a
- print(a)
结果:
- Traceback (most recent call last):
- File "<pyshell#5>", line 1, in <module>
- print(a)
- NameError: name 'a' is not defined
来源: http://www.bubuko.com/infodetail-2610437.html