[技术经验][Python] 比较两个字典 dictionaries 的 value

1. Background

Language: Python version 3.7

As of Python version 3.7, dictionaries are ordered. In Python 3.6 and earlier, dictionaries are unordered. from W3schools

Two dictionaries:

• same key number,
• different key name,
• different values.

dictionary_1 = {
  "key_1":  "val_1",
  "key_2":  "val_2",
  "key_3":  "val_3",
}

dictionary_2 = {
  "key_11":  "val_1",
  "key_21":  "val_21",
  "key_31":  "null",
}

Expectation:

(1) compare two dictionaries by key in sequence,
(2) if the value is different, then copy the key:value pairs into new dictionary.

2. Technical solution

2.1 flow chart

graph TD A(start) --> B[put dict_2 into one iterator] B --> C[loop dict_1 by its key] C --> D{end of loop?} D --> |Yes| Da[return dict_result] Da --> E(End) D --> |No| Db[get value_1 from dict_1 by key_1] Db --> F[get Key_2 from iterator; move to next one in the itrator] F --> G[get Value_2 via Key2] G --> H{Value1 != value_2} H --> |True| Ia[update key_1:value_2 in dict_result] H --> |False| Ib[do nothing] Ia --> C Ib --> C

2.2 Implementation

#####################################################################
# Description: 
#  (1) identify different value between dictionary_Ref and dictionary_Comp;
#  (2) copy the different value and its key;
#  (3) add the different value and its key into new dictionary_result.
# Arguments: 
#  (1) dict_Ref: dictionary, which is taken as Ref. 
#  (2) dict_Comp: dictionary, which is to compare. same length as dict_Ref.
#####################################################################
def compare_2_dictionaries(dict_Ref, dict_comp):

  dict_result = {}

  myiter = iter(dictionary_2)
  cnt_of_myiter = len(dictionary_2)

  for key_in_dict_1 in dictionary_1.keys():
    value_of_key_in_dict_1 = dictionary_1[key_in_dict_1]
    key_in_dict_2 = next(myiter)
    
    value_of_key_in_dict_2 = dictionary_2[key_in_dict_2] 

    if value_of_key_in_dict_1 != value_of_key_in_dict_2:
      dict_result.update({key_in_dict_1:value_of_key_in_dict_2})
    else:
      pass
  
  return dict_result

call above function:

compare_2_dictionaries(dictionary_1, dictionary_2)

output of the function:

{'key_2': 'val_21', 'key_3': 'null'}

3 Reference

3.1 dictionary

Ref_1: https://www.w3school.com.cn/python/python_dictionaries.asp
Ref_2: Https://docs.python.org/3/tutorial/datastructures.html#dictionaries

3.2 Iterator

Ref_1: https://www.w3school.com.cn/python/python_iterators.asp
Ref_2: https://docs.python.org/3/tutorial/classes.html#iterators

3.3 Markdown

Markdown 高级技巧