CODEWITHSUNDEEP
pythonpython-3.x
sandeep gunasekar
sandeep gunasekar

Reputation: 1

Search string value from a list with dictionary list values

Below I have a list and dict with the values as below. The dict has keys associated with list values.

What I wanted was to search strings in the list with values of the list in the dictionary and with each match capture the corresponding key value and create a new list with the key values for each match as above listed.

list = ['man', 'men', 'boy', 'buoy', 'cat','caat']
dict={'man':['man', 'men', 'mun'], 'boy':['boy','buoy','bay'], 'cat':['cat','caat','cut']}

Expected output for above case is: Outputlist=['man','man','boy','boy','cat','cat']

When I tried the same I am getting only one item to match as below.

lis = ['man', 'men', 'boy', 'buoy', 'cat','caat']
dic={'man':['man', 'men', 'mun'], 'boy':['boy','buoy','bay'], 'cat':['cat','caat','cut']}
for key,value in dic.items():
    if value in lis:
        output.append(key)
print(output)

Upvotes: 0

Views: 1574

Answers (3)

GabrielC
GabrielC

Reputation: 320

I think you did it the wrong way. First, you wan to go across the lis and after find the corresponding key : 

output = []
lis = ['man', 'men', 'boy', 'buoy', 'cat','caat']
dic={'man':['man', 'men', 'mun'], 'boy':['boy','buoy','bay'], 'cat':['cat','caat','cut']}
for l in lis:
    for key, value in dic.items():
        if l in value:
            output.append(key)
print(output)

As the others mention, you can use list comprehension to do it directly:

output = [next(k for k,v in dict if l in v) for l in list]

Upvotes: 0

Mateen Ulhaq
Mateen Ulhaq

Reputation: 27201

The first thing to note is that to achieve the same length input and output lists, you should be looping over the list, not the dictionary.

ys = [k for x in xs for k, v in d.items() if x in v]

Another way is to construct a reverse mapping. This should make things asymptotically faster:

lookup = {x: k for k, v in d.items() for x in v}

>>> lookup
{
 'bay': 'boy',
 'boy': 'boy',
 'buoy': 'boy',
 'caat': 'cat',
 'cat': 'cat',
 'cut': 'cat',
 'man': 'man',
 'men': 'man',
 'mun': 'man',
}

Then, simply:

ys = [lookup[x] for x in xs]

Upvotes: 1

Hozayfa El Rifai
Hozayfa El Rifai

Reputation: 1442

you can use a nested list comprehension. Notice that you should not use list and dict as variables:

x = [key for key, value in dict_.items() for x in list_ if x in value]
print(x) # ['man', 'man', 'boy', 'boy', 'cat', 'cat']

Upvotes: 5

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