在本教程中，我们将看到Python dict setDefault方法。
如果在else中存在，则使用Python字典setDefault方法返回值，如果提供了默认值，则在earters中插入具有值的键。

语法

dict.setdefault(key[, default_value])

返回

如果字典中存在键，则返回值，否则插入带值的键。

Python字典setDefault示例

示例1：如果在字典中存在键

listOfCountries={"Netherlands":"Delhi","China":"Beijing","Australia":"Canberra","UK":"London"}
#If key is present in dictionary
capital=listOfCountries.setdefault("China")
print("Capital of china:",capital)

输出：

Capital of china: Beijing

示例2：如果键出现在字典中，但不提供默认值

listOfCountries={"Netherlands":"Delhi","China":"Beijing","Australia":"Canberra","UK":"London"}
#If key is not present in dictionary and default is not provided
capital=listOfCountries.setdefault("USA")
print("Capital of USA:",capital)

输出：

Capital of USA: None

示例2：如果在字典中存在键，则提供默认值

listOfCountries={"Netherlands":"Delhi","China":"Beijing","Australia":"Canberra","UK":"London"}
#If key is not present in dictionary and default is provided
capital=listOfCountries.setdefault("USA","washigton")
print("Capital of USA:",capital)

输出：

Capital of USA: washigton