Python PCEP Lists Collections of Data

Python PCEP Lists Collections of Data

• 1.
  Module 2 Data Collections– Lists, Tuples, and Dictionaries Lists - collections of data
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  Module 2 Lists- collections of data Why do we need lists? var1 = int(input()) var2 = int(input()) var3 = int(input()) var4 = int(input()) var5 = int(input()) var6 = int(input()) : : declare such multi-value variables numbers = [10, 5, 7, 2, 1] List is a collection of elements, but each element is a scalar; the elements in a list are always numbered starting from zero.
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  Module 2 Lists- collections of data Indexing lists numbers = [10, 5, 7, 2, 1] print("Original list content:", numbers) # Printing original list content. numbers[0] = 111 print("nPrevious list content:", numbers) # Printing previous list content. numbers[1] = numbers[4] # Copying value of the fifth element to the second. print("New list content:", numbers) # Printing current list content. Original list content: [10, 5, 7, 2, 1] Previous list content: [111, 5, 7, 2, 1] New list content: [111, 1, 7, 2, 1]
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  Module 2 Lists- collections of data Accessing list content numbers = [10, 5, 7, 2, 1] # Accessing the list's first element. print(numbers[0]) numbers = [10, 5, 7, 2, 1] # Printing the list's length. print("List length:", len(numbers)) Each of the list's elements may be accessed separately. List length: 5
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  Module 2 Lists- collections of data Removing elements from a list numbers = [10, 5, 7, 2, 1] print("Original list content:", numbers) # Printing original list content. numbers[0] = 111 print("nPrevious list content:", numbers) # Printing previous list content. numbers[1] = numbers[4] # Copying value of the fifth element to the second. print("Previous list content:", numbers) # Printing previous list content. print("nList's length:", len(numbers)) # Printing previous list length. ### del numbers[1] # Removing the second element from the list. print("New list's length:", len(numbers)) # Printing new list length. print("nNew list content:", numbers) # Printing current list content. ### del: Any of the list's elements may be removed
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  Module 2 Lists- collections of data Negative indices are legal numbers = [111, 7, 2, 1] print(numbers[-1]) print(numbers[-2]) 1 2 an index -1 -> last one element in the list
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  Module 2 Lists- collections of data Functions vs. methods Function method A method is a specific kind of function; Invocvation: result = function(arg) Doesn't belong to any data Is owned by the whole code Function Invocation: result = data.method(arg) Is able to change the state of a selected entity Is owned by the data it works for Method
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  Module 2 Lists- collections of data append(), insert() numbers = [111, 7, 2, 1] print(len(numbers)) print(numbers) numbers.append(4) print(len(numbers)) print(numbers) numbers.insert(0, 222) print(len(numbers)) print(numbers) my_list = [] # Creating an empty list. for i in range(5): my_list.append(i + 1) print(my_list) • new element to the end of the existing list list.append(value) • add a new element at any place list.insert(location, value)
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  Module 2 Lists- collections of data Making use of lists my_list = [10, 1, 8, 3, 5] total = 0 for i in range(len(my_list)): total += my_list[i] print(total) my_list = [10, 1, 8, 3, 5] total = 0 for i in my_list: total += i print(total) 27 27
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  Module 2 Lists- collections of data Lists in action variable_1 = 1 variable_2 = 2 variable_2 = variable_1 variable_1 = variable_2 1 1 variable_1 = 1 variable_2 = 2 auxiliary = variable_1 variable_1 = variable_2 variable_2 = auxiliary 2 1 my_list = [10, 1, 8, 3, 5] my_list[0], my_list[4] = my_list[4], my_list[0] my_list[1], my_list[3] = my_list[3], my_list[1] print(my_list) [5, 3, 8, 1, 10] my_list = [10, 1, 8, 3, 5] length = len(my_list) for i in range(length // 2): my_list[i], my_list[length - i - 1] = my_list[length - i - 1], my_list[i] [5, 3, 8, 1, 10]
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  Module 2 Lists- collections of data Key takeaways The list is a type of data used to store multiple objects. Lists can be indexed and updated. List elements and lists can be deleted. Lists can be iterated through using the for loop. The len() function: to check the list's length Function, Method
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  Module 2 Lists- collections of data 21. The basics of lists 22. The basics of lists - the Beatles LAB Practice