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Python Lists

17th May 2023

In this tutorial, we will learn Python Lists

Python lists are ordered, mutable collections of items enclosed in square brackets ([]). They can store heterogeneous data types, such as integers, floats, strings, and even other lists. Lists are a fundamental data structure in Python and are commonly used for storing and manipulating collections of related values.

Here’s an example of a list containing various data types:

my_list = [1, 2, 'three', 4.5, True]

You can access individual elements in a list using indexing. Python uses zero-based indexing, so the first element is at index 0. Here’s an example:

print(my_list[0]) # Output: 1
print(my_list[2]) # Output: ‘three’

You can also use negative indexing to access elements from the end of the list. The last element has an index of -1, the second-to-last has an index of -2, and so on:

print(my_list[-1])  # Output: True
print(my_list[-3])  # Output: 'three'

Lists in Python are mutable, which means you can modify them by assigning new values to specific indexes:

my_list[1] = 'two'
print(my_list)  # Output: [1, 'two', 'three', 4.5, True]

You can perform various operations on lists, such as adding elements, removing elements, slicing, concatenating, and more. Here are some common list operations:

# Adding elements to a list
my_list.append('four')      # Adds 'four' at the end
my_list.insert(2, 'middle')  # Inserts 'middle' at index 2

# Removing elements from a list
my_list.remove('three')     # Removes the first occurrence of 'three'
popped_item = my_list.pop() # Removes and returns the last element

# Slicing a list
sliced_list = my_list[1:4]   # Returns a new list containing elements from index 1 to 3 (exclusive)

# Concatenating lists
new_list = my_list + [5, 6, 7]  # Combines two lists

# Length of a list
length = len(my_list)       # Returns the number of elements in the list

These are just a few examples of what you can do with lists in Python. They are versatile and widely used, providing a convenient way to work with collections of items.

Accessing elements from list

To access elements from a list in Python, you can use indexing or slicing. Here are a few examples:

  1. Indexing: You can access a specific element at a given index using square brackets []. Indexing starts from 0 for the first element.
my_list = [10, 20, 30, 40, 50]
print(my_list[0])  # Output: 10
print(my_list[2])  # Output: 30

2. Negative Indexing: You can also use negative indexing to access elements from the end of the list. -1 refers to the last element, -2 refers to the second-to-last element, and so on.

my_list = [10, 20, 30, 40, 50]
print(my_list[-1])  # Output: 50
print(my_list[-3])  # Output: 30

3. Slicing: You can retrieve a portion of the list using slicing. Slicing allows you to specify a range of indices to extract a sublist. The range is specified using the syntax [start:end], where start is the index of the first element (inclusive), and end is the index of the last element (exclusive).

my_list = [10, 20, 30, 40, 50]
print(my_list[1:4])  # Output: [20, 30, 40]
print(my_list[:3])   # Output: [10, 20, 30]
print(my_list[2:])   # Output: [30, 40, 50]

You can also specify a step value in the slice using [start:end:step]. This allows you to skip elements in the sublist.

my_list = [10, 20, 30, 40, 50]
print(my_list[::2])  # Output: [10, 30, 50]

These are some basic techniques for accessing elements from a list in Python. Remember that lists are mutable, so you can modify their elements using indexing and slicing as well.

Python Arrays

16th May 2023

In this tutorial, we will learn Arrays in Python Programming:

In Python, arrays can be implemented using several different data structures, depending on the specific requirements of your program. The built-in list type is the most commonly used and flexible data structure for creating arrays in Python. Lists are ordered, mutable (can be modified), and can contain elements of different data types. Here’s an example of creating and manipulating a list in Python:

# Creating a list
my_list = [1, 2, 3, 4, 5]
print(my_list)  # Output: [1, 2, 3, 4, 5]

# Accessing elements
print(my_list[0])  # Output: 1
print(my_list[2])  # Output: 3

# Modifying elements
my_list[3] = 10
print(my_list)  # Output: [1, 2, 3, 10, 5]

# Appending elements
my_list.append(6)
print(my_list)  # Output: [1, 2, 3, 10, 5, 6]

# Removing elements
my_list.remove(2)
print(my_list)  # Output: [1, 3, 10, 5, 6]

Another data structure commonly used for arrays in Python is the array module, which provides a more memory-efficient way of storing homogeneous data (elements of the same data type) compared to lists. Here’s an example:

import array

# Creating an array of integers
my_array = array.array('i', [1, 2, 3, 4, 5])
print(my_array)  # Output: array('i', [1, 2, 3, 4, 5])

# Accessing elements
print(my_array[0])  # Output: 1
print(my_array[2])  # Output: 3

# Modifying elements
my_array[3] = 10
print(my_array)  # Output: array('i', [1, 2, 3, 10, 5])

In addition to lists and arrays, there are other specialized data structures available in Python for handling arrays, such as NumPy arrays and pandas DataFrames, which offer more advanced functionality for numerical computing and data analysis tasks.

Adding Elements to a Array

To add elements to an array in Python, you can use the append() method or the + operator. Here’s how you can do it:

  1. Using append() method:
my_array = [1, 2, 3]  # Initial array
my_array.append(4)    # Add element 4 at the end
print(my_array)       # Output: [1, 2, 3, 4]

In this example, the append() method is called on the array my_array and passed the value 4 to add it to the end of the array.

2. Using the + operator:

my_array = [1, 2, 3] # Initial array 
my_array = my_array + [4] # Add element 4 at the end 
print(my_array)   # Output: [1, 2, 3, 4]

In this example, the + operator is used to concatenate the original array my_array with another list [4], resulting in a new array with the added element.

Both approaches achieve the same result of adding elements to an array. However, keep in mind that the append() method modifies the original array in-place, while using the + operator creates a new array. Choose the approach that best suits your needs based on whether you want to modify the original array or create a new one.

Accessing elements from the Array python

In Python, you can access elements from an array using their indices. The index represents the position of the element within the array, starting from 0 for the first element. Here’s how you can access elements from an array in Python:

# Define an array
my_array = [10, 20, 30, 40, 50]

# Access elements by index
print(my_array[0])  # Output: 10 (first element)
print(my_array[2])  # Output: 30 (third element)
print(my_array[-1])  # Output: 50 (last element)

# Update elements
my_array[1] = 25
print(my_array)  # Output: [10, 25, 30, 40, 50]

# Slicing arrays
print(my_array[1:4])  # Output: [25, 30, 40] (elements from index 1 to 3)
print(my_array[:3])  # Output: [10, 25, 30] (elements from start to index 2)
print(my_array[2:])  # Output: [30, 40, 50] (elements from index 2 to end)

You can access elements by specifying the index within square brackets []. Negative indices can be used to access elements from the end of the array. You can also update elements by assigning new values to the specified index. Slicing allows you to extract a subset of elements from the array by specifying a range of indices.

Python Tuples

16th May 2023

In this tutorial we wil learn tuples in Python:

Tuples are ordered, immutable sequences in Python. They are similar to lists but have some key differences. Here are some important points about tuples

  1. Creation : Tuples are created by enclosing comma-separated values in parentheses. For example:
my_tuple = (1, 2, 3)
empty_tuple = ()
single_value_tuple = (4,)

2. Accessing Elements : Individual elements of a tuple can be accessed using indexing, similar to lists. The indexing starts at 0. For example:

my_tuple = (1, 2, 3)
print(my_tuple[0])  # Output: 1

3. Immutable Nature:Tuples are immutable, meaning their elements cannot be changed after creation. However, if a tuple contains mutable objects (like lists), those objects can be modified. But you cannot reassign or modify the elements of a tuple directly.

4. Length and Membership: The len() function can be used to get the length of a tuple, and the in keyword can be used to check if an element is present in a tuple.

my_tuple = (1, 2, 3)
print(len(my_tuple))  # Output: 3

if 2 in my_tuple:
    print("2 is present in the tuple.")

5. Tuple Concatenation and Repetition: Tuples can be concatenated using the + operator, and repetition can be achieved using the * operator.

tuple1 = (1, 2, 3)
tuple2 = (4, 5, 6)
concatenated_tuple = tuple1 + tuple2
print(concatenated_tuple)  # Output: (1, 2, 3, 4, 5, 6)

repeated_tuple = tuple1 * 3
print(repeated_tuple)  # Output: (1, 2, 3, 1, 2, 3, 1, 2, 3)

6. Tuple Unpacking: Tuples can be unpacked into individual variables. The number of variables must match the number of elements in the tuple.

my_tuple = (1, 2, 3)
a, b, c = my_tuple
print(a)  # Output: 1
print(b)  # Output: 2
print(c)  # Output: 3

7. Returning Multiple Values: Tuples are commonly used to return multiple values from a function.

def get_name_and_age():
    name = "Alice"
    age = 25
    return name, age

name, age = get_name_and_age()
print(name)  # Output: Alice
print(age)   # Output: 25

Tuples are useful when you want to store a collection of items that should not be modified. They provide a lightweight alternative to lists in scenarios where immutability is desired.

Python Sets

16th May 2023

In this tutorial we will learn Sets in Python and its operation:

Python sets are unordered collections of unique elements. They are defined by enclosing a comma-separated sequence of values within curly braces ({}) or by using the built-in set() function.

Here’s an example of creating a set:

fruits = {"apple", "banana", "orange"}

In this example, the fruits set contains three elements: “apple”, “banana”, and “orange”. Notice that the order of the elements in a set is not guaranteed, and duplicates are automatically removed. If you print the set, the order of the elements may vary.

Sets have various operations and methods that can be performed on them. Some commonly used operations include:

1. Adding an element to a set:

fruits.add("mango")

2. Removing an element from a set:

fruits.remove("apple")

3. Checking if an element is present in a set:

if "banana" in fruits:
    print("Banana is in the set!")

4. Performing set operations like union, intersection, and difference:

set1 = {1, 2, 3}
set2 = {2, 3, 4}

union_set = set1 | set2  # union
intersection_set = set1 & set2  # intersection
difference_set = set1 - set2  # difference

print(union_set)            # {1, 2, 3, 4}
print(intersection_set)     # {2, 3}
print(difference_set)       # {1}

Sets are mutable, meaning you can add or remove elements from them. However, since sets are unordered, indexing and slicing operations are not supported. To iterate over the elements of a set, you can use a loop or convert it to a list.

Sets are often used when you need to store a collection of unique elements or perform operations such as finding common elements, removing duplicates, or checking membership efficiently.

Dictionary in Python

16th May 2023

In this tutorial, we will learn Dictionary in Python:

In Python, a dictionary is a built-in data structure that allows you to store and retrieve key-value pairs. It is also known as an associative array, map, or hash table in other programming languages. Dictionaries are mutable, unordered, and can contain elements of different data types.

Here’s a basic overview of how dictionaries work in Python:

  1. Creating a Dictionary: You can create a dictionary by enclosing comma-separated key-value pairs within curly braces {} or by using the built-in dict() function. Here’s an example:
# Creating an empty dictionary
my_dict = {}

# Creating a dictionary with initial values
my_dict = {"key1": value1, "key2": value2, "key3": value3}

# Using the dict() function
my_dict = dict(key1=value1, key2=value2, key3=value3)

2. Accessing Values:

You can access the values in a dictionary by using the corresponding key within square brackets []. If the key does not exist, it will raise a KeyError exception. Alternatively, you can use the get() method to retrieve values, which returns None or a default value if the key is not found.

# Accessing values
value1 = my_dict["key1"]
value2 = my_dict.get("key2")

3. Modifying Values:

You can modify the value associated with a key by assigning a new value to it.

my_dict["key1"] = new_value

4. Adding and Removing Items:

To add a new key-value pair, simply assign a value to a new key. To remove an item, you can use the del statement or the pop() method.

# Adding items
my_dict["key4"] = value4

# Removing items
del my_dict["key3"]
value = my_dict.pop("key2")

5. Dictionary Methods:

Python dictionaries come with several useful methods, including keys(), values(), and items(). These methods return iterable views of the dictionary’s keys, values, and key-value pairs, respectively.

# Iterating over keys
for key in my_dict.keys():
    print(key)

# Iterating over values
for value in my_dict.values():
    print(value)

# Iterating over key-value pairs
for key, value in my_dict.items():
    print(key, value)

Dictionaries are highly flexible and efficient for quick key-based lookups. They are widely used in Python for various purposes, such as counting occurrences, caching results, or organizing data.

Python String

16th May 2023

In this tutorial, we are going to learn Python String:

In Python, a string is a sequence of characters, enclosed within quotes. Strings can be created using single quotes ('...'), double quotes ("..."), or triple quotes ("""...""" or '''...'''). For example:

string1 = 'Hello, world!'
string2 = "This is a string."
string3 = '''This is a 
              multi-line 
              string.'''

In addition to creating strings, there are many built-in string methods in Python that allow you to manipulate and modify strings. For example, you can concatenate two strings using the + operator:

greeting = "Hello"
name = "John"
message = greeting + " " + name
print(message) # Output: Hello John

There are many more string methods and functions available in Python, which you can explore in the Python documentation.

Accessing characters in Python String

In Python, you can access individual characters in a string using indexing. Indexing starts from 0 for the first character and goes up to the length of the string minus one. To access a character at a specific index, you can use square brackets [] with the index inside.

For example, let’s say you have a string my_string = "Hello, World!":

my_string = "Hello, World!"
print(my_string[0])  # Output: H
print(my_string[4])  # Output: o
print(my_string[-1])  # Output: !

In the first example, my_string[0] returns the first character of the string, which is “H”. In the second example, my_string[4] returns the fifth character, which is “o”. In the third example, my_string[-1] returns the last character of the string, which is “!”. You can also use negative indexing to access characters from the end of the string, with -1 being the last character, -2 being the second to last character, and so on.

If you want to access a range of characters in a string, you can use slicing. Slicing uses the colon : operator to specify the start and end indices of the substring you want to extract. For example:

my_string = "Hello, World!"
print(my_string[0:5])  # Output: Hello
print(my_string[7:])  # Output: World!

In the first example, my_string[0:5] returns the substring from index 0 to index 4, which is “Hello”. In the second example, my_string[7:] returns the substring from index 7 to the end of the string, which is “World!”.

Reversing a Python String

To reverse a string in Python, you can use string slicing with a step of -1. Here is an example:

my_string = "hello world"
reversed_string = my_string[::-1]
print(reversed_string)

This will output:

dlrow olleh

In this example, [::-1] means “start at the end of the string, move to the beginning, and take each character with a step of -1 (i.e., backwards)”.

String Slicing

String slicing is a feature of many programming languages that allows you to extract a subset of characters from a string. It is a powerful tool for manipulating and analyzing strings, and can be used in a variety of ways.

In Python, for example, you can slice a string using the following syntax:

Syntex:
string[start:end:step]

where start is the index of the first character to include in the slice, end is the index of the first character to exclude from the slice, and step is the number of characters to skip between each character in the slice.

For example, the following code will extract the first three characters from a string:

string = "Hello, World!"
slice = string[0:3]
print(slice)

Output:

Hel

You can also use negative indices to count from the end of the string:

string = "Hello, World!"
slice = string[-6:-1]
print(slice)

Output:

World

You can omit the start or end index to slice from the beginning or end of the string, respectively:

string = "Hello, World!"
slice = string[:5]
print(slice)

slice = string[7:]
print(slice)

Output:
Hello
World!

Finally, you can use a step value to skip characters:

string = "Hello, World!"
slice = string[::2]
print(slice)

Output:
Hlo ol!

Note that the step value can also be negative, in which case the slice will be returned in reverse order:

string = "Hello, World!"
slice = string[::-1]
print(slice)

Output:
!dlroW ,olleH

Deleting/Updating from a String

To delete or update a string in Python, you can use string methods or slicing. Here are some examples:

  1. Deleting a substring from a string: You can use the replace() method to delete a substring from a string by replacing it with an empty string. For example:
string = "Hello World"
new_string = string.replace("World", "")
print(new_string)  # Output: "Hello "
  1. Updating a substring in a string: You can use slicing to update a substring in a string. For example:
string = "Hello World"
new_string = string[:5] + "Universe"
print(new_string)  # Output: "Hello Universe"

In the above example, the first five characters of the string (“Hello “) are combined with the new substring (“Universe”) to create a new string.

Note that strings are immutable in Python, which means you cannot modify a string in-place. Instead, you must create a new string that contains the desired modifications.

Formatting of Strings

In Python, you can format strings using various methods. Here are some common ways to format strings:

  1. Using the % operator: This is an older method available in Python and is similar to the C language’s printf-style formatting.
name = "Alice"
age = 25
print("My name is %s and I am %d years old." % (name, age))

Output:
My name is Alice and I am 25 years old.

2. Using the str.format() method: This method provides more flexibility and is recommended for newer versions of Python (Python 3 onwards).

name = "Alice"
age = 25
print("My name is {} and I am {} years old.".format(name, age))

Output:
My name is Alice and I am 25 years old.

You can also specify placeholders by index or name:

name = "Alice"
age = 25
print("My name is {0} and I am {1} years old. {0} {1}".format(name, age))

Output:
My name is Alice and I am 25 years old. Alice 25

3. Using f-strings (formatted string literals): This is a newer method introduced in Python 3.6, which provides a concise and readable way to format strings.

name = "Alice"
age = 25
print(f"My name is {name} and I am {age} years old.")

Output:
My name is Alice and I am 25 years old.

F-strings allow you to directly include variables and even evaluate expressions within curly braces.

a = 5
b = 3
print(f"The sum of {a} and {b} is {a + b}.")

Output:
The sum of 5 and 3 is 8.

These are just some of the most commonly used string formatting methods in Python. Each approach has its own advantages and can be used based on your preference and Python version.

Python String Built-In Function

Python provides a wide range of built-in functions that can be used to manipulate and operate on strings. Here are some commonly used string built-in functions:

  1. len(): Returns the length of a string. Example:
s = "Hello, World!"
length = len(s)
print(length)  # Output: 13

2. lower(): Converts all characters in a string to lowercase. Example:

s = "Hello, World!"
lower_case = s.lower()
print(lower_case)  # Output: hello, world!

3. upper(): Converts all characters in a string to uppercase. Example:

s = "Hello, World!"
upper_case = s.upper()
print(upper_case)  # Output: HELLO, WORLD!

4. strip(): Removes leading and trailing whitespace characters from a string. Example:

s = "   Hello, World!   "
stripped = s.strip()
print(stripped)  # Output: Hello, World!

5. split(): Splits a string into a list of substrings based on a delimiter. Example:

s = "Hello, World!"
split_list = s.split(", ")
print(split_list)  # Output: ['Hello', 'World!']

6. join(): Joins the elements of an iterable (e.g., list) into a single string using a specified delimiter. Example:

lst = ['Hello', 'World!']
joined_string = ", ".join(lst)
print(joined_string)  # Output: Hello, World!

7. replace(): Replaces all occurrences of a substring within a string with another substring. Example:

s = "Hello, World!"
replaced = s.replace("Hello", "Hi")
print(replaced)  # Output: Hi, World!

8. find(): Returns the index of the first occurrence of a substring within a string (-1 if not found). Example

s = "Hello, World!"
index = s.find("World")
print(index)  # Output: 7

These are just a few examples of Python’s string built-in functions. There are many more available that can help you manipulate and work with strings effectively.

Data Types in Python

16th May 2023

In this tutorial, we are going to learn Data Types in Python.

Python supports several built-in data types, which include:

  1. Numbers: There are two types of numbers in Python – integers and floating-point numbers.
  2. Strings: A string is a sequence of characters. Strings are used to represent text in Python.
  3. Lists: A list is a collection of elements, which can be of any data type. Lists are mutable, meaning they can be changed after creation.
  4. Tuples: A tuple is similar to a list, but is immutable, meaning it cannot be changed once it is created.
  5. Dictionaries: A dictionary is a collection of key-value pairs. Each key is associated with a value, and the keys must be unique.
  6. Sets: A set is an unordered collection of unique elements. Sets are useful when you want to perform operations like union, intersection, and difference on collections.
  7. Booleans: Booleans represent the truth values True and False. They are used to represent logical values in Python.
  8. None: None is a special type in Python that represents the absence of a value. It is commonly used to initialize variables or as a placeholder value.

In addition to these built-in data types, Python also allows you to define your own custom data types using classes.

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