What are the methods to get values ​​from python dictionary?

Python dictionary is a mutable container model that can store any amount of data of any type.

Each element in the dictionary consists of a key and a value, separated by a colon.

Dictionaries are usually used to store key-value pairs of data, such as storing records in a database.

The following are several methods of Python dictionary values ​​and their code demonstrations:

Method 1: Use square brackets [ ] operator

Use square brackets [ ] operator The corresponding value in the dictionary can be obtained by key.

# 定义一个字典
my_dict = {"name": "Tom", "age": 18, "gender": "male"}
 
# 获取字典中 "name" 键对应的值
value = my_dict["name"]
print(value)  # 输出：Tom

Method 2: Use the get() method

Use the get() method to get the corresponding value in the dictionary through the key. If the key does not exist, None is returned.

# 定义一个字典
my_dict = {"name": "Tom", "age": 18, "gender": "male"}
 
# 获取字典中 "name" 键对应的值
value = my_dict.get("name")
print(value)  # 输出：Tom
 
# 获取字典中 "phone" 键对应的值，由于 "phone" 不存在，返回 None
value = my_dict.get("phone")
print(value)  # 输出：None

Method 3: Use the items() method

Use the items() method to obtain all key-value pairs in the dictionary and return a list containing all key-value pairs. Each item in the list Element is a tuple, the first element of the tuple is the key and the second element is the value.

# 定义一个字典
my_dict = {"name": "Tom", "age": 18, "gender": "male"}
 
# 获取字典中所有键值对
items = my_dict.items()
print(items)  # 输出：dict_items([('name', 'Tom'), ('age', 18), ('gender', 'male')])
 
# 遍历所有键值对
for key, value in items:
    print(f"{key}: {value}")

Method 4: Use the keys() method

Use the keys() method to obtain all keys in the dictionary and return a list containing all keys.

# 定义一个字典
my_dict = {"name": "Tom", "age": 18, "gender": "male"}
 
# 获取字典中所有键
keys = my_dict.keys()
print(keys)  # 输出：dict_keys(['name', 'age', 'gender'])
 
# 遍历所有键
for key in keys:
    value = my_dict[key]
    print(f"{key}: {value}")

Method 5: Use the values() method

Use the values() method to get all the values ​​in the dictionary and return a list containing all values.

# 定义一个字典
my_dict = {"name": "Tom", "age": 18, "gender": "male"}
 
# 获取字典中所有值
values = my_dict.values()
print(values)  # 输出：dict_values(['Tom', 18, 'male'])
 
# 遍历所有值
for value in values:
    print

Method 6: Use the in keyword

Use the in keyword to determine whether a key is in the dictionary. If it is, it returns True, otherwise it returns False.

# 定义一个字典
my_dict = {"name": "Tom", "age": 18, "gender": "male"}
 
# 判断 "name" 是否在字典中
if "name" in my_dict:
    print("name is in my_dict")  # 输出：name is in my_dict
 
# 判断 "phone" 是否在字典中
if "phone" in my_dict:
    print("phone is in my_dict")
else:
    print("phone is not in my_dict")  # 输出：phone is not in my_dict

Method 7: Use the pop() method

Use the pop() method to delete the key-value pair of the specified key in the dictionary and return the corresponding value.

# 定义一个字典
my_dict = {"name": "Tom", "age": 18, "gender": "male"}
 
# 删除字典中 "age" 键的键值对，并返回对应的值
value = my_dict.pop("age")
print(value)  # 输出：18
print(my_dict)  # 输出：{"name": "Tom", "gender": "male"}

Method 8: Use the popitem() method

Use the popitem() method to delete any key-value pair in the dictionary and return the corresponding key-value pair. What is returned is a element Group, the first element of the tuple is the key and the second element is the value.

# 定义一个字典
my_dict = {"name": "Tom", "age": 18, "gender": "male"}
 
# 删除字典中的任意一个键值对，并返回对应的键值对
key, value = my_dict.popitem()
print(key, value)  # 输出：gender male
print(my_dict)  # 输出：{"name": "Tom", "age": 18}

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