通过比较两个长度不等的字典和相似的键来更新字典的值

Question

I have a list of characters from the list character_list = ['A', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'K', 'L', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'V', 'W', 'Y'] which I am using to track the number of character occurrences in a given string . My approach is to make a dictionary that has each character in character_list as its key and its count as the value. If a character within character_list is not present within string then its value will be None

I have a string which I used to make a dictionary to count the frequency of each character within the string.

from collections import  Counter

character_list = ['A', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'K', 'L', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'V', 'W', 'Y']

string ='LDPQKLFWWWWWWWWWWWWWWWWWDKIRERNDCEQGHILYKMFPSTRTKRCQTSGGGPHDGPQDLDRELFKLKQMGKDMNTFPNFTFEDPKFE'

string_counts = dict(sorted((Counter(string)).items(), key=lambda tuple_element: tuple_element[0] ) )

string_counts yields:

{'C': 2, 'D': 8, 'E': 5, 'F': 7, 'G': 6, 'H': 2, 'I': 2, 'K': 8, 'L': 6, 'M': 3, 'N': 3, 'P': 6, 'Q': 5, 'R': 5, 'S': 2, 'T': 5, 'W': 17, 'Y': 1}

Since not all characters in string are in string_counts , character_list and string_count are of different lengths and won't have all the same keys. This makes constructing the dictionary difficult.

To get around this I tried making a dictionary of Boolean Values, where if the character is present in both string and character_list the value will be True and None if the character is not present in string in order to make them both the same length. I did that using zip and cycle

from itertools import cycle

bool_dict = dict()

for string_count_letter, char_letter in zip( cycle( string_counts.keys() ), character_list):

    if char_letter in string_counts.keys():
        bool_dict[char_letter] = True
    else :
        bool_dict[char_letter] = None
print(bool_dict)

bool_dict yields:

{'A': None, 'C': True, 'D': True, 'E': True, 'F': True, 'G': True, 'H': True, 'I': True, 'K': True, 'L': True, 'M': True, 'N': True, 'P': True, 'Q': True, 'R': True, 'S': True, 'T': True, 'V': None, 'W': True, 'Y': True}

Then from here I want my final dictionary to be:

dict_i_want = {'A': None, 'C': 2, 'D': 8, 'E': 5, 'F': 7, 'G': 6, 'H': 2, 'I': 2, 'K': 8, 'L': 6, 'M': 3, 'N': 6, 'P': 6, 'Q': 5, 'R': 2, 'S': 5, 'T': 5, 'V': None,'W':17,'Y':1}
}

but using this code that updates bool_dict values if the value is True to the frequency of a character within ``string``` gets me a dictionary that mismatches the frequencies to the wrong character:

string_count_values = list(string_counts.values())
bool_values = list(bool_dict.values())
bool_keys = list(bool_dict.keys())

for  string_count_v, bool_v, bool_k in zip(  cycle(string_count_values),bool_values , bool_keys ):

    print(bool_v)
    if bool_v == True :

        bool_dict[bool_k] = string_count_v

print(bool_dict) 
bool_dict{'A': None, 'C': 8, 'D': 5, 'E': 7, 'F': 6, 'G': 2, 'H': 2, 'I': 8, 'K': 6, 'L': 3, 'M': 3, 'N': 6, 'P': 5, 'Q': 5, 'R': 2, 'S': 5, 'T': 17, 'V': None, 'W': 2, 'Y': 8} # this is wrong

#compared to 
dict_i_want = {'A': None, 'C': 2, 'D': 8, 'E': 5, 'F': 7, 'G': 6, 'H': 2, 'I': 2, 'K': 8, 'L': 6, 'M': 3, 'N': 6, 'P': 6, 'Q': 5, 'R': 2, 'S': 5, 'T': 5, 'V': None,'W':17,'Y':1}
}
# this is right

Answer 1

All you need:

from collections import  Counter

character_list = ['A', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'K', 'L', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'V', 'W', 'Y']

string ='LDPQKLFWWWWWWWWWWWWWWWWWDKIRERNDCEQGHILYKMFPSTRTKRCQTSGGGPHDGPQDLDRELFKLKQMGKDMNTFPNFTFEDPKFE'

c = Counter(string)

dict_i_want = {k: None if k not in c else c[k] for k in character_list}
print(dict_i_want)

Result:

{'A': None, 'C': 2, 'D': 8, 'E': 5, 'F': 7, 'G': 6, 'H': 2, 'I': 2, 'K': 8, 'L': 6, 'M': 3, 'N': 3, 'P': 6, 'Q': 5, 'R': 5, 'S': 2, 'T': 5, 'V': None, 'W': 17, 'Y': 1}

What I'd prefer:

dict_i_want = {k: 0 if k not in c else c[k] for k in character_list}

And then even this works:

dict_i_want = {k: c[k] for k in character_list}

Because a Counter returns 0 for a key that's not in it anyway.

(By the way, naming a variable string shadows the Python module string - not used very commonly these days, but you may want to avoid shadowing it all the same and use a more descriptive name for a variable, eg sample )