How to search if dictionary value contains certain string with Python

Question

I have a dictionary with key-value pair. My value contains strings. How can I search if a specific string exists in the dictionary and return the key that correspond to the key that contains the value.

Let's say I want to search if the string 'Mary' exists in the dictionary value and get the key that contains it. This is what I tried but obviously it doesn't work that way.

#Just an example how the dictionary may look like
myDict = {'age': ['12'], 'address': ['34 Main Street, 212 First Avenue'],
          'firstName': ['Alan', 'Mary-Ann'], 'lastName': ['Stone', 'Lee']}

#Checking if string 'Mary' exists in dictionary value
print 'Mary' in myDict.values()

Is there a better way to do this since I may want to look for a substring of the value stored ('Mary' is a substring of the value 'Mary-Ann').

Answer 1

You can do it like this:

#Just an example how the dictionary may look like
myDict = {'age': ['12'], 'address': ['34 Main Street, 212 First Avenue'],
      'firstName': ['Alan', 'Mary-Ann'], 'lastName': ['Stone', 'Lee']}

def search(values, searchFor):
    for k in values:
        for v in values[k]:
            if searchFor in v:
                return k
    return None

#Checking if string 'Mary' exists in dictionary value
print search(myDict, 'Mary') #prints firstName

Answer 2

I am a bit late, but another way is to use list comprehension and the any function, that takes an iterable and returns True whenever one element is True :

# Checking if string 'Mary' exists in the lists of the dictionary values
print any(any('Mary' in s for s in subList) for subList in myDict.values())

If you wanna count the number of element that have "Mary" in them, you can use sum():

# Number of sublists containing 'Mary'
print sum(any('Mary' in s for s in subList) for subList in myDict.values())

# Number of strings containing 'Mary'
print sum(sum('Mary' in s for s in subList) for subList in myDict.values())

From these methods, we can easily make functions to check which are the keys or values matching.

To get the keys containing 'Mary':

def matchingKeys(dictionary, searchString):
    return [key for key,val in dictionary.items() if any(searchString in s for s in val)]

To get the sublists:

def matchingValues(dictionary, searchString):
    return [val for val in dictionary.values() if any(searchString in s for s in val)]

To get the strings:

def matchingValues(dictionary, searchString):
    return [s for s i for val in dictionary.values() if any(searchString in s for s in val)]

To get both:

def matchingElements(dictionary, searchString):
    return {key:val for key,val in dictionary.items() if any(searchString in s for s in val)}

And if you want to get only the strings containing "Mary", you can do a double list comprehension :

def matchingStrings(dictionary, searchString):
    return [s for val in dictionary.values() for s in val if searchString in s]

Answer 3

Klaus solution has less overhead, on the other hand this one may be more readable

myDict = {'age': ['12'], 'address': ['34 Main Street, 212 First Avenue'],
          'firstName': ['Alan', 'Mary-Ann'], 'lastName': ['Stone', 'Lee']}

def search(myDict, lookup):
    for key, value in myDict.items():
        for v in value:
            if lookup in v:
                return key

search(myDict, 'Mary')

Answer 4

import re
for i in range(len(myDict.values())):
     for j in range(len(myDict.values()[i])):
             match=re.search(r'Mary', myDict.values()[i][j])
             if match:
                     print match.group() #Mary
                     print myDict.keys()[i] #firstName
                     print myDict.values()[i][j] #Mary-Ann

Answer 5

>>> myDict
{'lastName': ['Stone', 'Lee'], 'age': ['12'], 'firstName': ['Alan', 'Mary-Ann'],
 'address': ['34 Main Street, 212 First Avenue']}

>>> Set = set()

>>> not ['' for Key, Values in myDict.items() for Value in Values if 'Mary' in Value and Set.add(Key)] and list(Set)
['firstName']

Answer 6

For me, this also worked:

def search(myDict, search1):
    search.a=[]
    for key, value in myDict.items():
        if search1 in value:
            search.a.append(key)

search(myDict, 'anyName')
print(search.a)

• search.a makes the list a globally available
• if a match of the substring is found in any value, the key of that value will be appended to a

Answer 7

Following is one liner for accepted answer ... (for one line lovers ..)

def search_dict(my_dict,searchFor):
    s_val = [[ k if searchFor in v else None for v in my_dict[k]] for k in my_dict]    
    return s_val

Answer 8

To provide a more general solution for others using this post to do similar or more complex python dictionary searches: you can use dictpy

import dictpy

myDict = {'age': ['12'], 'address': ['34 Main Street, 212 First Avenue'],
          'firstName': ['Alan', 'Mary-Ann'], 'lastName': ['Stone', 'Lee']}

search = dictpy.DictSearch(data=myDict, target='Mary-Ann')
print(search.result)   # prints -> [firstName.1, 'Mary-Ann']  

The first entry in the list is the target location: dictionary key "firstName" and position 1 in the list. The second entry is the search return object.

The benefit of dictpy is it can find multiple 'Mary-Ann' and not just the first one. It tells you the location in which it found it, and you can search more complex dictionaries (more levels of nesting) and change what the return object is.