Python DSA Cheat-sheet for SuperHeros

 # Python Cheat Sheet for Data Structures and Algorithms  # List and Tuple Operations  # Creating a list or tuple my_list = [1, 2, 3, 4] # use square brackets for lists my_tuple = (5, 6, 7, 8) # use parentheses for tuples  # Accessing elements by index first = my_list[0] # get the first element of the list (index 0) last = my_tuple[-1] # get the last element of the tuple (index -1)  # Slicing a list or tuple sublist = my_list[1:3] # get a sublist from index 1 (inclusive) to index 3 (exclusive) subtuple = my_tuple[:2] # get a subtuple from the beginning to index 2 (exclusive) reversed_list = my_list[::-1] # get a reversed list using negative step  # Concatenating two lists or tuples new_list = my_list + [9, 10] # create a new list by adding another list new_tuple = my_tuple + (11, 12) # create a new tuple by adding another tuple  # Repeating a list or tuple repeated_list = my_list * 2 # create a new list by repeating the original list twice repeated_tuple = my_tuple * 3 # create a new tuple by repeating the original tuple three times  # Checking membership of an element is_in_list = 3 in my_list # returns True if 3 is in the list, False otherwise is_in_tuple = 9 in my_tuple # returns False if 9 is not in the tuple, True otherwise  # Iterating over a list or tuple for x in my_list: # loop through each element x in the list  print(x) # print x  for i, x in enumerate(my_tuple): # loop through each index i and element x in the tuple  print(i, x) # print i and x  # Unpacking a list or tuple a, b, c, d = my_list # assign each element of the list to a variable e, f, g, h = my_tuple # assign each element of the tuple to a variable  

 # List methods (do not apply to tuples) my_list.append(5) # add an element 5 at the end of the list my_list.insert(2, 6) # insert an element 6 at index 2 of the list my_list.remove(4) # remove the first occurrence of element 4 from the list my_list.pop() # remove and return the last element of the list my_list.pop(1) # remove and return the element at index 1 of the list my_list.index(3) # return the index of the first occurrence of element 3 in the list my_list.count(2) # return the number of times element 2 appears in the list my_list.sort() # sort the list in ascending order (modify the original list) my_list.reverse() # reverse the order of the list (modify the original list) my_list.copy() # return a shallow copy of the list my_list.clear() # remove all elements from the list  

 # Creating a dictionary my_dict = {"name": "Alice", "age": 25, "gender": "female"} # use curly braces and colons for dictionaries  # Accessing values by keys name = my_dict["name"] # get the value associated with the key "name" age = my_dict.get("age") # get the value associated with the key "age" or None if not found  # Adding or updating key-value pairs my_dict["email"] = "alice@gmail.com" # add a new key-value pair to the dictionary my_dict["age"] = 26 # update the value associated with the key "age"  # Removing key-value pairs del my_dict["gender"] # delete the key-value pair with the key "gender" from the dictionary email = my_dict.pop("email") # remove and return the value associated with the key "email" name, age = my_dict.popitem() # remove and return an arbitrary key-value pair as a tuple  # Checking membership of a key is_in_dict = "name" in my_dict # returns True if "name" is a key in the dictionary, False otherwise  # Iterating over a dictionary for key in my_dict: # loop through each key in the dictionary  print(key) # print key  for value in my_dict.values(): # loop through each value in the dictionary  print(value) # print value  for key, value in my_dict.items(): # loop through each key-value pair in the dictionary  print(key, value) # print key and value  # Unpacking a dictionary into variables name, age, gender = my_dict # assign each key of the dictionary to a variable {"name": name, "age": age, "gender": gender} = my_dict # assign each value of the dictionary to a variable  

 my_dict.keys() # return a view object of the keys of the dictionary my_dict.values() # return a view object of the values of the dictionary my_dict.items() # return a view object of the key-value pairs of the dictionary my_dict.update({"city": "New York", "age": 27}) # update the dictionary with another dictionary or iterable my_dict.copy() # return a shallow copy of the dictionary my_dict.clear() # remove all key-value pairs from the dictionary  

 # Creating a set my_set = {1, 2, 3, 4} # use curly braces for sets (but no colons) empty_set = set() # use the set() function to create an empty set  # Adding or removing elements my_set.add(5) # add an element 5 to the set my_set.remove(4) # remove an element 4 from the set (raises KeyError if not found) my_set.discard(3) # remove an element 3 from the set (does nothing if not found) my_set.pop() # remove and return an arbitrary element from the set (raises KeyError if empty) my_set.clear() # remove all elements from the set  # Checking membership of an element is_in_set = 2 in my_set # returns True if 2 is in the set, False otherwise  # Iterating over a set for x in my_set: # loop through each element x in the set  print(x) # print x  

 my_string = " Hello, World! " # Length of a string length = len(my_string) print(length) # Output: 19  # Splitting a string into a list my_list = my_string.split(" ") print(my_list) # Output: ['', '', '', 'Hello,', 'World!', '', '', '']  # Joining elements of a list into a string my_string = " ".join(my_list) print(my_string) # Output: Hello, World!  # Checking if a substring exists in a string if "Hello" in my_string: print("Substring found!") # Output: Substring found!  # Replacing occurrences of a substring new_string = my_string.replace("World", "Python") print(new_string) # Output: Hello, Python!  # Converting a string to lowercase/uppercase lowercase = my_string.lower() uppercase = my_string.upper() print(lowercase) # Output: hello, world! print(uppercase) # Output: HELLO, WORLD!  # Checking if a string starts/ends with a specific substring starts_with_hello = my_string.startswith("Hello") ends_with_exclamation = my_string.endswith("!") print(starts_with_hello) # Output: False print(ends_with_exclamation) # Output: True  # Removing leading/trailing whitespace from a string stripped_string = my_string.strip() print(stripped_string) # Output: Hello, World!  # Checking if a string is alphanumeric is_alphanumeric = my_string.isalnum() print(is_alphanumeric) # Output: False  # Counting occurrences of a substring count = my_string.count("Hello") print(count) # Output: 1