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').

score 41 · Answer 1 · answered Jun 27 '13 at 10:44

41

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

answered Jun 27 '13 at 10:44

Klaus Byskov Pedersen

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1

what will be performance issue in this, if suppose I have 1 million records and I'm implementing this for Auto complete search. – Chetan Sharma May 29 '15 at 08:38
1

@Unknown You should definitely not do this for your case. You need to index the values in a separate reverse lookup dictionary. – wisbucky Aug 18 '15 at 00:14
7

Alternatively, if you know the dictionary is huge, you could convert it to JSON and perform a regex search such as `pattern = r'\w+(?=": [\S\s][^:]+{})'.format(search_text)` to get the key. It won't be faster for smaller dictionaries, but it will be for larger ones, in particular when the data is in the worst case position – Erik Jan 06 '17 at 21:47

Naeio · Accepted Answer · 2021-02-08T10:08:38.190

22

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]

edited Feb 08 '21 at 10:08

answered May 16 '20 at 22:09

Naeio

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For getting the keys, based on the dictionary used by the user in the question it returns this error message ` in (.0) ----> 1 print (sum(1 for key,val in myDict if 'Mary' in val) > 0) ValueError: too many values to unpack (expected 2)` and is the same for the `matchingKeys` function ` in (.0) 1 def matchingKeys(dictionary, searchString): ----> 2 return [key for key,val in dictionary if searchString in val] ValueError: too many values to unpack (expected 2)` – Andrea Ciufo Feb 07 '21 at 15:55
1

@AndreaCiufo Oops my bad, I forgot to use the method `dict.items`. I wanted to give the concept, the idea of using one line list comprehension but by reading it all over again, I realize I have made many mistakes – Naeio Feb 08 '21 at 09:50
1

yep this happens because there is a list of strings associated with keys and not a single string :) – Andrea Ciufo Feb 08 '21 at 15:16
1

Exactly, and I forgot the `dict.items` :) IDK what I was thinking about when writing my answer, I guess I went too fast – Naeio Feb 11 '21 at 23:53
1

How might someone search multiple strings? using this approach – paranormaldist Apr 01 '21 at 23:29
1

@paranormaldist Well, you have to take a list or tuple of strings as input and then compare each string of the dict to each string in the input. So that would mean replacing `any(searchString in s for s in val)` by `any(any(searched in s) for s in val for searched in searchString)` or something like that. But it gets quite long on only one line, so maybe you should better do it on multiple lines or divide it into functions – Naeio Apr 09 '21 at 01:50

score 11 · Answer 3 · answered Jun 27 '13 at 11:05

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')

score 4 · Answer 4 · answered Jun 27 '13 at 11:07

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

thefourtheye · Answer 5 · 2013-06-27T11:06:02.340

2

>>> 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']

edited Jun 27 '13 at 11:06

answered Jun 27 '13 at 10:51

thefourtheye

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score 2 · Answer 6 · answered Nov 01 '17 at 11:05

2

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

answered Nov 01 '17 at 11:05

Shushiro

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I just learned, that search.a is not a smart way to make a globally available. currently working it out, this may help: http://python-textbok.readthedocs.io/en/1.0/Variables_and_Scope.html – Shushiro Nov 01 '17 at 11:36
solution found via:https://stackoverflow.com/questions/7129285/why-would-you-use-the-return-statement-in-python – Shushiro Nov 01 '17 at 11:43
def search(myDict, search1): a=[] for key, value in myDict.items(): if search1 in value: a.append(key) return a x=search(myDict, 'anyName') print(str(x)) – Shushiro Nov 01 '17 at 11:48
def search(myDict, search1): a=[] for key, value in myDict.items(): if search1 in value: a.append(key) return a x=search(myDict, 'anyName') print(str(x)) – Shushiro Nov 01 '17 at 11:48

score 1 · Answer 7 · answered Feb 15 '18 at 10:28

1

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

answered Feb 15 '18 at 10:28

shantanu pathak

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Ah, gotcha. You _could_ do it in one line like this: `search_dict = lambda x, y: ((k if y in v else None for v in x[k]) for k in x)` – MazeOfEncryption Jul 07 '18 at 17:46
I get an error `list indices must be integers or slices, not list` – Andrea Ciufo Feb 07 '21 at 12:53
@AndreaCiufo give ur code .. i think you dict contains multiple values in a single key.. – shantanu pathak Feb 10 '21 at 09:19
I used the question code, and actually contains a list of strings and was similar to @Nei oversight [here](https://stackoverflow.com/a/61844241/6290211) :) – Andrea Ciufo Feb 10 '21 at 10:54
@AndreaCiufo is the problem fixed now ? – shantanu pathak Mar 05 '21 at 02:45

score 1 · Answer 8 · answered Oct 17 '21 at 20:31

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.

score 0 · Answer 9 · answered Jun 28 '13 at 18:43

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

Armando Sodano · Answer 10 · 2015-03-10T15:27:45.800

0

def search(myDict, lookup):
    a=[]
    for key, value in myDict.items():
        for v in value:
            if lookup in v:
                 a.append(key)
    a=list(set(a))
    return a

if the research involves more keys maybe you should create a list with all the keys

edited Mar 10 '15 at 15:27

answered Mar 09 '15 at 17:49

Armando Sodano

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score -3 · Answer 11 · answered Jan 09 '19 at 21:21

-3

import json 'mtach' in json.dumps(myDict) is true if found

answered Jan 09 '19 at 21:21

Amer

1

4

I think the formatting in your answer is a bit off. Take a look at https://stackoverflow.com/editing-help – Ivo Merchiers Jan 09 '19 at 21:52

How to search if dictionary value contains certain string with Python

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