Python how do I append to every string in list using lambda function?

January 31, 2022

I’m trying to learn about lambda functions, I’m would like the code to:

add a slash ‘/’ to the end of a string in list ‘techCodeList’
add and append every item in ‘finishList’ to the every entry in ‘techCodeList’, appending to ‘combinedCodeList’ every time (so combinedCodeList = [‘a/ABUL’, ‘a/BEL’, ‘a/PBL’] etc)

I could do it using other methods but I want to try using lambda, so would it be viable and if so how would I do it? My code is below:

#example shortened
class myClass:
    def __init__(self):
        self.techCodeList = ('a','b','c')

        def applyCodes(self):
                self.combinedCodeList = list()
                finishList = ["ABUL","BEL","PBL","PBUL","ABL","SBL","SBSL","SBUL","PNP","SNP","PCP","SCP","NBP","ASP","ACP","SAL","SAS","AMB","CBP","HBN","MBL","MWL","HBB","SPE","PBUL/SAMPLE"]#list to append to techcodelist
                len1 = len(self.combinedCodeList)
                arrayCounter = 0
                for i in self.techCodeList:
                    for _ in finishList:
                        print (arrayCounter)
                        self.techCodeList = list(map(lambda orig_string: orig_string + '/', self.techCodeList[arrayCounter]))
                        self.techCodeList = list(map(lambda orig_string: orig_string + finishList[arrayCounter], self.techCodeList[arrayCounter]))
                        self.combinedCodeList.append(self.techCodeList[arrayCounter])
                        if arrayCounter == len(self.techCodeList) - 1:
                            break
                        arrayCounter = arrayCounter + 1

                print (self.combinedCodeList)

myClass()

And here is the result in the combinedCodeList:

[‘aABUL’, ‘/BEL’, ‘/BEL’, ‘/BEL’]

If you have any other suggestions for good habits or suggestions for my code please feel free to leave them too, I’m still very much learning. Thanks.

>Solution :

If I understood correctly you want to create an exchaustive combinations between all the entries from the tech code and finish lists.

For that you can use list comprehension like below:

tech_code_list = ["a", "b", "c"]
finish_list = ["ABUL","BEL","PBL","PBUL","ABL","SBL","SBSL","SBUL","PNP","SNP","PCP","SCP","NBP","ASP","ACP","SAL","SAS","AMB","CBP","HBN","MBL","MWL","HBB","SPE","PBUL/SAMPLE"]
               

combined_code_list = [
    tech_code + "/" + finish for tech_code in tech_code_list for finish in finish_list
]

print(combined_code_list) 
# will print: ['a/ABUL', 'a/BEL', 'a/PBL', 'a/PBUL', ... ]