Dictionary
Definition
- One of the data structure in python.
- has key and value bined. You can fine value when you know the key
- very slimier with hashmap
Data Structures in Python
- List
- Tuple
- Dictionary
- set
declaration
- use { and } to declare
- the value can be list
- the key can be int or string. But not list. (TypeError: unhashable type: ‘list’)
dictionary={"key1":"value1","key2":"value2","key3":"value3"}
how to use
- indexing like List
- get() method
difference between the indexing and get method
If key does not exist, the indexing will return error. But get method will return None.
# List처럼 인덱스를 넣기
print(dictionary["key1"]) # value1
print(dictionary["key2"]) # value2
print(dictionary["key3"]) # value3
# print(dictionary["key4"]) # KeyError: 'key4' means there is no key
# get() 메서드를 사용
print(dictionary.get("key1")) # value1
print(dictionary.get("key2")) # value2
print(dictionary.get("key3")) # value3
print(dictionary.get("key4")) # return None, it does not cause error