Python - Searching multiple values in list and performing multiple operations

Question

I'm trying to search a list I have for specific values and if any of those values exist in the list, I would like to perform a different operation.

Currently this is the list I am working with:

print(categories)
['Creams', 'Bath', 'Personal Care']

What I would like to do is search this categories list for some different values. To do this, I've converted categories into a set and am individually searching for each of the values with an if statement.

For example:

c = set(categories)
if "Conditioners" in c:
     print("1")
if "Bath" in c: 
     print("2")
if "Shaving Gels" in c:
     print("3")

Which returns:

What I would ideally like to do is put my criteria into a list or some other relevant data structure and have it perform that particular operation if that value exists within categories in an efficient manner.

why not have the keywords in a dictionary that maps to functions that execute on the categories? — modesitt
– modesitt, Commented Aug 2, 2018 at 14:12

Andrej Kesely · Accepted Answer · 2018-08-02 14:15:55Z

6

You can store your functions in dictionary, where values are desired functions. That way, you have easy access to them by keys and you can traverse categories normally:

categories = ['Creams', 'Bath', 'Personal Care']

my_dict = {
    'Conditioners': lambda: print(1),
    'Bath': lambda: print(2),
    'Shaving Gels': lambda: print(3)
}


for category in categories:
    fn = my_dict.get(category, lambda: None)
    fn()

Output:

answered Aug 2, 2018 at 14:15

Andrej Kesely

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3 Comments

express_v2 Over a year ago

This is what I was looking for. Thank you!

express_v2 Over a year ago

Would you happen to know how I could do a different function if in the categories list, two or more of the keys in my_dict values as opposed to each individual function?

Andrej Kesely Over a year ago

@express_v2 That's a little bit more complicated and the answer is long for comments. Feel free to open new question.

W Stokvis · Accepted Answer · 2018-08-02 14:22:26Z

2

IIUC, this is what you're looking for. dict comprehension with enumerate. This will also reduce the amount of manual labor required so long as your list is in the order you want.

d = {k:v for v,k in enumerate(categories,1)}
d
{'Creams': 1, 'Bath': 2, 'Personal Care': 3}

You can perform whatever operation you want on the dictionary.

c = ['Conditioners','Bath','Shaving Gels']
for i in c:
    print (d.get(i, None))
None
2
None

edited Aug 2, 2018 at 14:22

answered Aug 2, 2018 at 14:14

W Stokvis

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Comments

Luke Polson · Accepted Answer · 2018-08-02 14:24:22Z

1

Probably a dictionary would be a suitable datatype. You could complete your task like such.

diction = {"Conditioners": 1, "Bath": 2} #add whatever else you want

for item in categories:
        try:
           print(diction[item])
        except:
            continue

edited Aug 2, 2018 at 14:24

answered Aug 2, 2018 at 14:17

Luke Polson

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Comments

scharette · Accepted Answer · 2018-08-02 15:01:56Z

I'd like to suggest another neat and maintainable alternative to dictionaries. You could also create a class with @staticmethod and use getattr to call methods like so,

categories = ['Creams', 'Bath', 'Personal Care']

class CategoriesWorker:
    @staticmethod
    def Creams():
        print(1)
    @staticmethod
    def Bath():
        print(2)
    @staticmethod
    def PersonalCare():
        print(3)

for category in categories:
    try:
        getattr(CategoriesWorker, category.replace(" ", ""))()
    except AttributeError:
        pass

>>>
1
2
3

Note here that naming of your @staticmethods is crucial. I basically use a the same value without spaces and then strip them of the actual value in the list to retrieve it in the class.

Basically, I suggested this in order to overcome the problem where using a dictionary in conjunction with lambdas could lead to unreadable code. Indeed, your specific example ask to simply print() values. But what if the logic of the methods was more complicated ? You'd be writing a unreadable dictionary fast enough.

Now, an alternative you be to wrap the logic in a method and use it in a dictionary.

categories = ['Creams', 'Bath', 'Personal Care','test']
def Creams():
  print(1)

def Bath():
  print(2)

def PersonalCare():
  print(3)

comparison_dict = {'Creams':Creams,'Bath':Bath,'Personal Care':PersonalCare}


for category in categories:
  comparison_dict.get(category, lambda: None)()

>>>>
1
2
2

That would be valid also. I just like the class definition better since it is clear what this class intends to do and I like to have related code at one compact emplacement.

Hearner · Accepted Answer · 2018-08-02 14:19:01Z

0

categories = ['Creams', 'Bath', 'Personal Care']
criteria = {"Conditioners" : "1", "Bath" : "2", "Shaving Gels" : "3"}

# loop through all the categories
for i in set(categories):
    # if the category is in the criteria print the value
    if i in criteria.keys():
        print(criteria[i]) #print 2

answered Aug 2, 2018 at 14:19

Hearner

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Comments

whackamadoodle3000 · Accepted Answer · 2018-08-02 14:21:59Z

0

Something like this (for the exact case you put above)

a=['Creams', 'Bath', 'Personal Care']
b=['Conditioners','Bath','Shaving Gels']
[print(c-1) for c,e in b if e in enumerate(a)]

answered Aug 2, 2018 at 14:21

whackamadoodle3000

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