Dictionary

docs 참고

• 정렬되지 않은 값들을 넣는다
• map과같이 값들을 저장
• key, value 쌍으로 이루어짐
• key는 unique

생성

• { } (braces)으로 생성
• comma로 구분
• mixed key로 생성가능

defualtdict

• from collections import defaultdict
• dict클래스의 subclass이다
• 차이점은 keyerror를 일으키지 않는다
• defaultvalue를 제공

dic_list=default(list)
for src,target in tickets:
    dic_lista[src].append(target)

sorted vs sort

• sort는 자체적으로 리스트를 정렬
• sorted는 정렬하여 새로운 리스트 생성

dictionary 정렬

1. key 기준 정렬

   sorted(dic_list.keys())
   

2. key,value 알파벳순 정렬

   sorted(dic_list)
   

3. key, value 기준으로 정렬 => value,key순서대로

   sorted(dic_list.items(),key=lambda x : (x[1],x[0]))
   

정렬

• 정렬문서 참고
• sorted(sorted(count_dict.keys()), key=lambda x: count_dict[x])
• 내림 차순 정렬 reverse=True 추가
• sorted(iterable,key,reverse)

• sorted

    count_dict = {}  
    for num in row:  
    if num == 0:  
    continue  
    if num in count_dict:  
    count_dict[num] += 1  
    else:  
    count_dict[num] = 1  
    next_row = []  
    for key in sorted(sorted(count_dict.keys()), key=lambda x: count_dict[x]):  
    next_row.append(key)  
    next_row.append(count_dict[key])  
    next_arr.append(next_row)  
    max_len = max(max_len, len(next_row)  
    sorted(sorted(count_dict.keys()), key=lambda x: count_dict[x]):  
  

접근

• key로 접근가능
• ex) Dict[‘name’]=1
• get 메소드로 접근가능
• ex) Dict.get(‘name’)=1

삭제

• key로 삭제가능

    # Initial Dictionary  
    Dict = { 5 : 'Welcome', 6 : 'To', 7 : 'Geeks',  
    'A' : {1 : 'Geeks', 2 : 'For', 3 : 'Geeks'},  
    'B' : {1 : 'Geeks', 2 : 'Life'}}  
    print("Initial Dictionary: ")  
    print(Dict)  
      
    # Deleting a Key value  
    del Dict[6]  
    print("\nDeleting a specific key: ")  
    print(Dict)  
      
    # Deleting a Key from  
    # Nested Dictionary  
    del Dict['A'][2]  
    print("\nDeleting a key from Nested Dictionary: ")  
    print(Dict)  
  

• pop 메소드 : 출력 후 그 key에해당하는 값 삭제

    # Creating a Dictionary  
    Dict = {1: 'Geeks', 'name': 'For', 3: 'Geeks'}  
      
    # Deleting a key  
    # using pop() method  
    pop_ele = Dict.pop(1)  
    print('\nDictionary after deletion: ' + str(Dict))  
    print('Value associated to poped key is: ' + str(pop_ele))  
  

• popitem 메소드 : 임의의 key에 해당하는 key,value 삭제

    #### Creating Dictionary  
    Dict = {1: 'Geeks', 'name': 'For', 3: 'Geeks'}  
      
    #### Deleting an arbitrary key  
    ##### using popitem() function  
    pop_ele = Dict.popitem()  
    print("\nDictionary after deletion: " + str(Dict))  
    print("The arbitrary pair returned is: " + str(pop_ele))  
  

  clear () : 모든 값 삭제

METHODS DESCRIPTION

• copy() They copy() method returns a shallow copy of the dictionary.
• clear() The clear() method removes all items from the dictionary.
• pop() Removes and returns an element from a dictionary having the given key.
• popitem() Removes the arbitrary key-value pair from the dictionary and returns it as tuple.
• get() It is a conventional method to access a value for a key.
• dictionary_name.values() returns a list of all the values available in a given dictionary.
• str() Produces a printable string representation of a dictionary.
• update() Adds dictionary dict2’s key-values pairs to dict
  setdefault() Set dict[key]=default if key is not already in dict
• keys() Returns list of dictionary dict’s keys
• items() Returns a list of dict’s (key, value) tuple pairs
• has_key() Returns true if key in dictionary dict, false otherwise
• fromkeys() Create a new dictionary with keys from seq and values set to value.
• type() Returns the type of the passed variable.
• cmp() Compares elements of both dict.