How to replace the items from given dictionary? - python-3.x

Question

I am a newbie in python. I was playing with dictionaries and wanted to know the solution to the given problem
list_ = [['any', 'window', 'says', 'window'], ['dog', 'great'], ['after', 'end', 'explains', 'income', '.', '?']]
dictionary=[('dog', 'cat'), ('window', 'any')]
def replace_matched_items(word_list, dictionary):
int_word = []
int_wordf = []
for lst in word_list:
for ind, item in enumerate(lst):
for key,value in dictionary:
if item in key:
lst[ind] = key
else:
lst[ind] = "NA"
int_word.append(lst)
int_wordf.append(int_word)
return int_wordf
list_ = replace_matched_items(list_, dictionary)
print(list_ )
Output generated is:
[[['NA', 'window', 'NA', 'window'], ['NA', 'NA'], ['NA', 'NA', 'NA', 'NA', 'NA', 'NA']]]
The expected output is:
[[['NA', 'window', 'NA', 'window'], ['dog', 'NA'], ['NA', 'NA', 'NA', 'NA', 'NA', 'NA']]]
I am using python 3
Thanks in advance

Answer 1

Some quick introduction to data structures in python just to clarify your question.
A list is similar to your arrays, where they can be accessed via their index and are mutable meaning items within the list can be changed. Lists are generally identified by brackets [].
For example:
my_array = [4, 8, 16, 32]
print(my_array[0]) # returns 4
print(my_array[3]) # returns 32
my_array[2] = 0
print(my_array) # returns [4, 8, 0, 32]
A tuple is similar to a list, however, the main difference is that they are immutable meaning items within the tuple cannot be changed. Items can still be accessed via their index. They are generally identified by parenthesis ().
For example:
my_tuple = ('this', 'is', 'a', 'tuple', 'of', 'strings')
print(my_tuple[0]) # returns 'this'
my_tuple[1] = 'word' # throws a 'TypeError' as items within tuples cannot be changed.
A dictionary uses a key and value pair to access, store, and change data in a dictionary. Similar to lists, they are mutable, however, each value has their own unique key. To access a value in the dictionary, you have to pass the key within the dictionary. Dictionaries are generally identified by curly braces {}.
For Example:
my_dictionary = {'John':13, 'Bob':31, 'Kelly':24, 'Ryan':17}
print(my_dictionary['Kelly']) # Returns 24
my_dictionary['Kelly'] = 56 # Assigns 56 to Kelly
print(my_dictionary['Kelly']) # Returns 56
The key:value takes this form within the dictionary, and each subsequent key-value pairs are separated by commas.
I would highly suggested reading the official documentation on the Data Structures available for python: Link Here
To answer the question
From your code given, you've used a tuple with your key-value pair encapsulated the tuple in a list as your dictionary data structure.
Your expected output is a result of you iterating through the entire dictionary, and did not handle what will occur once you've found the key for your dictionary. This can be fixed by adding a break statement within your if-statement once a key has been found.
The break statement, will exit your for loop once a key has been found and, will continue onto the next list item.
Your function will end up looking like:
def replace_matched_items(word_list, dictionary):
int_word = []
int_wordf = []
for lst in word_list:
for ind, item in enumerate(lst):
for key,value in dictionary:
if item in key:
lst[ind] = key
break
else:
lst[ind] = "NA"
int_word.append(lst)
int_wordf.append(int_word)
return int_wordf
Suggested to use a Dictionary
Using a Dictionary data structure for your key and value pairs will let you have access to methods that'll let you check whether a key exists inside your dictionary.
If you have a list of keys, and you'd like to check if a dictionary key exists within a list:
this_list = ['any', 'window', 'says', 'window', 'dog',
'great', 'after', 'end', 'explains', 'income', '.', '?']
dictionary = {'dog':'cat', 'window':'any'}
matched_list = []
for keys in dictionary:
if keys in this_list:
matched_list.append(keys) # adds keys that are matched
else:
# do something if the key is in not the dictionary
print(matched_list)
# Returns ['dog', 'window']