""" ========== 1.7 sets ========== .. important:: This lesson is still under development. """ #%% md # A set is a collection of objects just like lists with the exception that it # is unordered, does not contain same objects more than once, and can not # contain immutable objects like lists. # # A set can be created from an existing sequence object such as a string, # list or tuple. #%% urdu = set("National language of Pakistan") print(type(urdu)) print(urdu) #%% pak_langs = set(["Balochi", "Barohi", "Sindhi", "Balti"]) print(pak_langs) #%% md # If our sequence contains repeating objects, only one instance of those repeating # objects will be included in the list. #%% pak_langs = set(("Balochi", "Barohi", "Sindhi", "Balti", "Balochi")) print(pak_langs) #%% md # Although, we can create sets from lists, but a set can not contain a list as an object. #%% pak_langs = set((("Balochi", "Barohi"), ("punbabi", "siraiki"))) print(pak_langs) #%% # uncomment following line # pak_langs = set((["Balochi", "Barohi"], ["punbabi", "siraiki"])) print(pak_langs) #%% md # In second case above, we want our set to have two lists as objects, so the error was prompted. # Sets are mutable i.e. they can be changed. We can add new objects in sets as following #%% pak_langs = set(["Balochi", "Barohi", "Sindhi"]) pak_langs.add("Pashto") print(pak_langs) #%% md # There are immutable sets as well with the name `frozenset`. #%% balochistan_langs = frozenset(["Balochi", "Barohi", "Pashto"]) # uncomment following line # balochistan_langs.add("punjabi") #%% md # Operations on sets #%% md # adding elements # ----------------- # We saw, how to add objects in sets with the method `add`. We can not violate # aforementioned rules using `add` method. #%% imperialists = {"bbc", "cnn"} # uncomment following line # imperialists.add(["voa","dw"]) # TypeError #%% imperialists.add('bbc') print(imperialists) #%% imperialists.update(["voa","dw"]) print(imperialists) #%% imperialists = {"bbc", "cnn"} # uncomment following line # imperialists.update([["voa","dw"]]) # TypeError print(imperialists) #%% md # ``|`` operator can also be used to add/concatenate two sets #%% imperialists = {"bbc", "cnn"} imperialists | {"voa", "dw"} #%% imperialists = {"bbc", "cnn"} imperialists |= {"voa", "dw"} print(imperialists) #%% md # `clear` # ---------- # We can clear the contents of a set by using the method `clear` on a set. #%% dakus = {"musharaf", "nawaz", "benazir"} dakus.clear() # after NRO (https://en.wikipedia.org/wiki/National_Reconciliation_Ordinance) print(dakus) #%% md # Copy # ------ # The assignment operation ``=`` does not create a new set. #%% more_dakus = {"pervaiz elahi", "altaf husain"} dakus_backup = more_dakus more_dakus.clear() print(dakus_backup) #%% md # ``copy`` method creates a shallow copy #%% more_dakus = {"pervaiz elahi", "altaf husain"} dakus_backup = more_dakus.copy() more_dakus.clear() print(dakus_backup) #%% imperialists = {"BBC", "CNN", "VOA"} more_imperialists = imperialists.copy() more_imperialists.add("DW") print(imperialists) print(more_imperialists) #%% md # ``difference`` # ---------------- #%% pml_q = {"zafrullah jamali", "fawad hussain", "pervaiz elahi", "umar ayyub"} pml_n = {"choi Nisar" , "umar ayyub", "khawaja Asif"} pti = {"firdows ashiq", "umar ayyub", "asad umar", "fawad hussain"} pml_q.difference(pti) #%% lotas_2013 = pml_q.difference(pml_q.difference(pml_n)) print(lotas_2013) #%% md # We can also make use of ``-`` operator #%% print(pml_q - pti) #%% md # `difference_update` # ----------------------- # This makes change in original set. similar to `x-y` with the exception that `x` # is itself changed. #%% pml_q = {"zafrullah jamali", "fawad hussain", "pervaiz elahi", "umar ayyub"} pml_n = {"choi Nisar" , "umar ayyub", "khawaja Asif"} pti = {"firdows ashiq", "umar ayyub", "asad umar", "fawad hussain"} pml_q.difference_update(pml_n) print(pml_q) #%% pml_q.difference_update(pti) print(pml_q) #%% md # ``discard`` # --------------- # removes an element from set if it is present. #%% pml_q = {"zafrullah jamali", "fawad hussain", "pervaiz elahi", "umar ayyub"} pml_q.discard("zafrullah jamali") print(pml_q) #%% pml_q.discard("choi nisar") print(pml_q) #%% md # `ferdows ashiq` is not present in set `musharaf` but using `discard` did not # raise an error. ## ``remove`` # Same as `discard` with the exception that an error is raised if the object is # not present in set. #%% pml_q = {"zafrullah jamali", "fawad hussain", "pervaiz elahi", "umar ayyub"} pml_q.remove("zafrullah jamali") print(pml_q) #%% # uncomment following line # pml_q.remove("choi nisar") # KeyError print(pml_q) #%% md # ``pop`` # -------- #%% pml_q = {"firdows ashiq", "fawad hussain", "pervaiz elahi", "umar ayyub"} pml_q.pop() print(pml_q) #%% pml_q.pop() print(pml_q) #%% md # Running the above cell multiple times will eventually raise an error when the # set becomes empty. # %% # `union` # ------------- #%% pml_q = {"firdows ashiq", "fawad hussain", "pervaiz elahi", "umar ayyub"} pml_n = {"choi Nisar" , "umar ayyub", "khawaja Asif"} pml_q.union(pml_n) #%% print(pml_q | pml_n) #%% md ## `intersection` #%% pml_q = {"firdows ashiq", "fawad hussain", "pervaiz elahi", "umar ayyub"} pti = {"firdows ashiq", "umar ayyub", "asad umar", "fawad hussain"} pml_q.intersection(pti) #%% md # We can also use ``&`` operator #%% print(pml_q & pti) #%% md # The original set `pml_q` remains unchanged. #%% print(pml_q) #%% md # However, if we use `intersection_update`, the original set is changed #%% pml_q.intersection_update(pti) print(pml_q) #%% md # If we want to find out intersection between multiple sets, we can do it as following. #%% pml_q = {"firdows ashiq", "fawad hussain", "pervaiz elahi", "umar ayyub"} pti = {"firdows ashiq", "umar ayyub", "asad umar", "fawad hussain"} pml_n = {"choi Nisar" , "umar ayyub", "khawaja Asif"} sets = [pml_q, pml_n, pti] set.intersection(*sets) #%% md # or #%% sets = [pml_n, pti] pml_q.intersection(*sets) #%% md # So we can say that `umar ayyub `_ # is the most consistent turncoat. # %% # `isdisjoint` # -------------- # returns `True` if the intersection of two sets is not empty set. #%% ppp = {"firdows ashiq", "fawad hussain", "Amin Faheem", "umar ayyub"} pti = {"firdows ashiq", "umar ayyub", "asad umar", "fawad hussain"} ji = {"liaquat baloch", "siraj ul haq", "munawar hasan"} ppp.isdisjoint(ji) #%% ppp.isdisjoint(pti) #%% md # `issubset` # ------------ # ``<`` is used for proper subset and ``<=`` is used for subset checking. #%% pml_n = {"nawaz", "shahbaz", "pervaiz elahi", "mushahid husain"} pml_q = {"pervaiz elahi", "mushahid husain"} pml_q.issubset(pml_n) #%% print(pml_q <= pml_n) #%% print(pml_q < pml_q) # %% md # ``issuperset`` # -------------- # ``>`` is used for proper superset and ``>=`` is used for superset checking. #%% pml_n = {"nawaz", "shahbaz", "pervaiz elahi", "mushahid husain"} pml_q = {"pervaiz elahi", "mushahid husain"} pml_n.issuperset(pml_q) #%% print(pml_n >= pml_q) #%% print(pml_n > pml_n) #%% md # Since sets are unordered, the operation ``in`` is faster when applied to # sets as compared to lists. #%% print("nawaz" in pml_n) #%% print("nawaz" not in pml_q)