Python Dictionary setdefault()用法及代碼示例

字典 setdefault() 方法

setdefault() 方法用於獲取具有指定鍵的項目的值，如果指定的鍵在字典中不存在，則設置項目(鍵，值)。

用法:

    dictionary_name.setdefault(key, value)

參數：

• key– 指定要返回設置其值的鍵名。
• value– 可選參數，默認值為None，如果 key 不存在，value成為指定鍵的值。

返回值：

該方法的返回類型是值的類型，它返回指定鍵的值。

注意:如果value未定義，它返回None。

例：

# Python Dictionary setdefault() Method with Example

# dictionary declaration
student = {
  "roll_no":101,
  "name":"Shivang",
  "course":"B.Tech",
  "perc":98.5
}

# printing dictionary
print("data of student dictionary...")
print(student)

# getting value of 'roll_no'
x = student.setdefault('roll_no', 0)
print('roll_no:', x)

# getting value of address key
# that does not exist, then function
# inserts given key & value
x = student.setdefault('address', 'New Delhi')
print('address:', x)

# printing dictionary
print("data of student dictionary after setdefault()...")
print(student)

# getting value of age key
# that does not exist, then function
# inserts given key & None
x = student.setdefault('age')
print('age:', x)

# printing dictionary
print("data of student dictionary after setdefault()...")
print(student)

輸出

data of student dictionary...
{'roll_no':101, 'name':'Shivang', 'course':'B.Tech', 'perc':98.5}
roll_no: 101
address: New Delhi
data of student dictionary after setdefault()...
{'roll_no':101, 'name':'Shivang', 'course':'B.Tech', 'perc':98.5, 'address':'New Delhi'}
age: None
data of student dictionary after setdefault()...
{'roll_no':101, 'name':'Shivang', 'course':'B.Tech', 'perc':98.5, 'address':'New Delhi', 'age':None}