Recursive string compare in Python

Question

I have to compare 2 lists of strings fetched from the database and from a CSV file respectively.

The data objects could vary in length.

The condition

if obj1 >= obj2 the perform the code. but since the data can vary in length I have to hard code every possibility according to the length of the objects, which is tiring and wrong.

According to the code if a obj1 length is greater than obj2 length then perform the program.

Can you please tell me a way where I can compare a string of length 8 and length 4 (example numbers) without hard coding it through if else. I believe this is achievable through while loop. Which is sadly my weak point. and this comparison goes until the first character is reached and when WHILE reaches 0 it breaks.

Meaning if I get an object of length 2 and the other object length is 3, How can I perform recursive compressing of the objects through while loop.

HELP would be greatly appreciated.

I hope you get the question.

def LCR():
    dest = Destination.objects.values_list('dest_num', flat=True)
# This method turn the fetched data into a list. Example
#['1233','4412','23135','123']
    rates = {}
    ratelist = {}



    csv_file = open(r'.\adoc.csv')



    data_set = csv_file.read().decode("UTF-8")
    io_string = io.StringIO(data_set)
    next(io_string)

    for column in csv.reader(io_string, delimiter=str(u",")):
        rates[column[0]] = column[1]
#Example data
#['8523654','754','4563']



    for desNum in dest:
        desNum = str(desNum)
        # print type(desNum)


        for venNum, venValue in rates.items():
            venlen = len(venNum)
            deslen = len(desNum)
            if venlen >= deslen:



                if desNum[:-1] == venNum[:-1] and desNum[:-2] == venNum[:-2] and desNum[:-3] == venNum[:-3]:
                    print (venNum)
                    print (desNum)
                    # print "Works well"
                    # print ('====================')

                    ratelist[venNum] = venValue




                elif desNum[:-1] == venNum[:-2] and desNum[:-2] == venNum[:-3] and desNum[:-3] == venNum[:-4]:

                    # ratelist[venNum] = venValue
                    print (venNum)
                    print (desNum)


                elif desNum[:-1] == desNum[:-3] and desNum[:-2] == venNum[:-4] and desNum[:-3] == venNum[:-5]:

                    # ratelist[venNum] = venValue
                    print (venNum)
                    print (desNum)



                elif desNum[:-1] == venNum[:-4] and desNum[:-2] == venNum[:-5]:

                    # ratelist[venNum] = venValue
                    print (venNum)
                    print (desNum)


                elif desNum[:-1] == venNum[:-5] and desNum[:-2] == venNum[:-6]:
                    # ratelist[venNum] = venValue
                    print (venNum)
                    print (desNum)
            else:
                print "LENGTH ERROR"
    print ratelist

Looks like you just want to know if venNum starts with desNum? — Iain Shelvington
– Iain Shelvington, Commented Jul 25, 2019 at 7:24
starts from the end side yes. But since the length could be different I can't use -5 or -3 etc like that. Or can I? — Djang000
– Djang000, Commented Jul 25, 2019 at 7:28
You can just do if venNum.startswith(desNum) rather than all of those nested if statements — Iain Shelvington
– Iain Shelvington, Commented Jul 25, 2019 at 7:30
I have to make sure the sequence matches. if [:-1] == [:-1] and [:-2] == [:-2] and [:-3]==[:-3] . . . . . Something like that — Djang000
– Djang000, Commented Jul 25, 2019 at 7:32

Berkay Tekin Öz · Accepted Answer · 2019-07-25 08:08:48Z

Since I couldn't understand what exactly is the question, I guess you want to check one of these conditions.

If you would like to know if string1 contains string2 you could do:

if string2 in string1:
    # Do what you want to do

string2 in string1 will return True if string1 contains string2.

Or

if string1.find(string2) != -1:
    # Do what you want to do

string1.find(string2) will return the index string2 occurs in string1. If string2 couldn't be found, it returns -1.

If you would like to know if string1 starts or ends with string2 you could do:

if string1.startswith(string2):
    # Do what you want to do

if string1.endswith(string2):
    # Do what you want to do

So in your case string1 would be equal to the venNum and string2 would be equal to the desNum. You could implement it like this:

if venNum in desNum:
    # Do what you want to do

if venNum.find(desNum) != -1:
    # Do what you want to do

if venNum.startswith(desNum):
    # Do what you want to do

if venNum.endswith(desNum):
    # Do what you want to do

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