Python classes to Ammu

Python uses dynamic typing, meaning you can reassign variables to different data types. This makes Python very flexible in assigning data types; it differs from other languages that are statically typed. We can use a colon(:) to perform slicing which grabs everything up to a designated point. s='Hello world' print(s[:5])=Hello we can use two colons in a row and then a number specifying the frequency to grab elements. For example: s[::2] 'HloWrd' s[::3] 'Hlwl' s[::-1] 'dlroW olleH' .split() is a Built in string method used to split the string, by default it takes the blank spaces s='please split this function' s.split() ['please','split','this','function'] Split by a specific element by using that letter s.split('f') ['please split this', 'unction'] We can use the .format() method to add formatted objects to printed string statements. print('Insert another string with curly brackets: {}'.format('The inserted string')) 'Insert another string with curly brackets: The inserted string' print('Insert another {0} with curly brackets: {1}'.format('string','The inserted string')) Insert another string with curly brackets: The inserted string There are three ways to perform string formatting. •The oldest method involves placeholders using the modulo % character. print("I'm going to inject %s text here, and %s text here." %('some','more')) I'm going to inject some text here, and more text here. •An improved technique uses the .format() string method. 'String here {} then also {}'.format('something1','something2') print('The {2} {1} {0}'.format('fox','brown','quick')) print('First Object: {a}, Second Object: {b}, Third Object: {c}'.format(a=1,b='Two',c=12.3)) print('A %s saved is a %s earned.' %('penny','penny')) # vs. print('A {p} saved is a {p} earned.'.format(p='penny')) •The newest method, introduced with Python 3.6, uses formatted string literals, called f-strings name = 'Fred' print(f"He said his name is {name}.") Pass !r to get the string representation: print(f"He said his name is {name!r}") He said his name is 'Fred' Lists Earlier when discussing strings we introduced the concept of a sequence in Python. Lists can be thought of the most general version of a sequence in Python. Unlike strings, they are mutable, meaning the elements inside a list can be changed! my_list = [1,2,3] my_list = ['A string',23,100.232,'o'] my_list = ['one', 'two', 'three', 4, 5] You would have to reassign the list to make the change permanent. my_list = my_list + ['add new item permanently'] ['one', 'two', 'three', 4, 5, 'add new item permanently'] Use the append method to permanently add an item to the end of a list: list1.append('append me!') List1 = [1, 2, 3, 'append me!'] Use pop to "pop off" an item from the list. By default pop takes off the last index, but you can also specify which index to pop off. Nesting Lists A great feature of Python data structures is that they support nesting. This means we can have data structures within data structures. For example: A list inside a list. # Let's make three lists lst_1=[1,2,3] lst_2=[4,5,6] lst_3=[7,8,9] # Make a list of lists to form a matrix matrix = [lst_1,lst_2,lst_3] o/p matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]] Dictionaries We've been learning about sequences in Python but now we're going to switch gears and learn about mappings in Python. If you're familiar with other languages you can think of these Dictionaries as hash tables. So what are mappings? Mappings are a collection of objects that are stored by a key, unlike a sequence that stored objects bytheir relative position. This is an important distinction, since mappings won't retain order since they have objects defined by a key. A Python dictionary consists of a key and then an associated value. That value can be almost any Python object. my_dict = {'key1':123,'key2':[12,23,33],'key3':['item0','item1','item2']} my_dict['key3'] = ['item0','item1','item2'] Tuples In Python tuples are very similar to lists, however, unlike lists they are immutable meaning they cannot be changed. You would use tuples to present things that shouldn't be changed, such as days of the week, or dates on a calendar. t = ('one',2) Because of this immutability, tuples can't grow. Once a tuple is made we cannot add to it. Sets Sets are an unordered collection of unique elements. We can construct them by using the set() function. Let's go ahead and make a set to see how it works list1 = [1,1,2,2,3,4,5,6,1,1] ; set(list1) = {1, 2, 3, 4, 5, 6} my_file1 = open('C:\\Users\\acer\\Desktop\\read.txt','a+') my_file1.write('\n This is a newly added line') my_file1.seek(0) print(my_file1.read()) if 1 > 0: print("hhh) print() elif 2>1: print else: print j = 0 for i in range(0,10): j = j+i print(j) list1 = [1,2,3,4,5] list1 = list1 + [sum(list1)] print(list1) for letter in 'This is a string.': print(letter) list2 = [(2,4),(6,8),(10,12)] t = 0 for t1 in list2: t = t + t1[0] print(t)