Python Programming Common Built In Functions And Methods Complete Guide

Python Built-in Functions

1. print()

The print() function outputs the specified message to the console.

# Example:
print("Hello, World!")

2. type()

The type() function returns the type of the specified object.

# Example:
x = 5
print(type(x))  # Output: <class 'int'>
y = "Hello"
print(type(y))  # Output: <class 'str'>

3. len()

The len() function returns the number of items in an object like a string, list, or tuple.

# Example:
text = "Python"
print(len(text))  # Output: 6
numbers = [1, 2, 3, 4, 5]
print(len(numbers))  # Output: 5

4. range()

The range() function generates a sequence of numbers.

# Example:
for i in range(5):
    print(i)  # Outputs: 0 1 2 3 4

# Using range(start, stop, step)
for i in range(1, 6, 2):
    print(i)  # Outputs: 1 3 5

5. input()

The input() function takes input from the user.

# Example:
name = input("Enter your name: ")
print(f"Hello {name}")

6. int(), float(), str()

These functions convert one data type to another.

# Example:
num_str = "10"
num_int = int(num_str)
print(num_int)  # Output: 10 (as an integer)

num_float = float(num_str)
print(num_float)  # Output: 10.0 (as a float)

num_back_to_str = str(num_int)
print(num_back_to_str)  # Output: "10" (as a string)

7. list(), tuple(), set(), dict()

These functions convert sequences (like strings, tuples, lists) into lists, tuples, sets, or dictionaries respectively.

# Example:
string_example = "hello"
list_example = list(string_example)
print(list_example)  # Output: ['h', 'e', 'l', 'l', 'o']

tuple_example = (1, 2, 3)
list_from_tuple = list(tuple_example)
print(list_from_tuple)  # Output: [1, 2, 3]

numbers = [1, 2, 2, 3, 4, 4, 5]
unique_numbers = set(numbers)
print(unique_numbers)  # Output: {1, 2, 3, 4, 5}

keys_values = [('key1', 'value1'), ('key2', 'value2')]
dictionary_example = dict(keys_values)
print(dictionary_example)  # Output: {'key1': 'value1', 'key2': 'value2'}

8. max(), min(), sum()

These functions are used to find the maximum, minimum, and sum of a sequence respectively.

# Example:
numbers = [1, 5, 9, 2, 8]
print(max(numbers))  # Output: 9
print(min(numbers))  # Output: 1
print(sum(numbers))  # Output: 25

9. sorted()

The sorted() function returns a new sorted list from the elements of any sequence.

# Example:
numbers = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]
sorted_numbers = sorted(numbers)
print(sorted_numbers)  # Output: [1, 1, 2, 3, 3, 4, 5, 5, 5, 6, 9]

# Sorting in reverse order
reverse_sorted_numbers = sorted(numbers, reverse=True)
print(reverse_sorted_numbers)  # Output: [9, 6, 5, 5, 5, 4, 3, 3, 2, 1, 1]

10. abs()

The abs() function returns the absolute value of a number, which is its distance from zero.

# Example:
number = -20
print(abs(number))  # Output: 20

Python String Methods

1. upper() and lower()

The upper() method converts all characters to uppercase, and lower() method converts all characters to lowercase.

# Example:
greeting = "Hello, World!"
print(greeting.upper())  # Output: HELLO, WORLD!
print(greeting.lower())  # Output: hello, world!

2. strip(), rstrip(), lstrip()

These methods remove leading and trailing whitespaces.

# Example:
text = "   Hello, World!   "
print(text.strip())  # Output: "Hello, World!"
print(text.rstrip())  # Output: "   Hello, World!"
print(text.lstrip())  # Output: "Hello, World!   "

3. replace()

The replace() method replaces a certain substring within a string.

# Example:
message = "Hi, I am Hi"
new_message = message.replace("Hi", "Hello")
print(new_message)  # Output: "Hello, I am Hello"

4. split()

The split() method splits a string into a list.

# Example:
sentence = "Hello, World!"
words = sentence.split(", ")
print(words)  # Output: ["Hello", "World!"]

5. join()

The join() method concatenates the elements of a list into a single string.

# Example:
words = ["Hello", "World!"]
sentence = ", ".join(words)
print(sentence)  # Output: "Hello, World!"

6. find()

The find() method returns the index of the first occurrence of the specified value.

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

Python List Methods

1. append()

The append() method adds a single element to the end of the list.

# Example:
numbers = [1, 2, 3]
numbers.append(4)
print(numbers)  # Output: [1, 2, 3, 4]

2. remove()

The remove() method removes the first occurrence of a value from the list.

# Example:
numbers = [1, 2, 2, 3, 4, 5]
numbers.remove(2)
print(numbers)  # Output: [1, 2, 3, 4, 5]

3. pop()

The pop() method removes the item at the specified index and returns it. If no index is specified, it removes the last item.

# Example:
numbers = [1, 2, 3, 4, 5]
popped_element = numbers.pop()
print(popped_element)  # Output: 5
print(numbers)  # Output: [1, 2, 3, 4]

popped_element_2 = numbers.pop(1)
print(popped_element_2)  # Output: 2
print(numbers)  # Output: [1, 3, 4]

4. insert()

The insert() method inserts a specified value at the specified position.

# Example:
numbers = [1, 2, 4, 5]
numbers.insert(2, 3)
print(numbers)  # Output: [1, 2, 3, 4, 5]

5. reverse()

The reverse() method reverses the elements of the list in place.

# Example:
numbers = [1, 2, 3, 4, 5]
numbers.reverse()
print(numbers)  # Output: [5, 4, 3, 2, 1]

6. sort()

The sort() method sorts the list in place and does not return anything.

# Example:
numbers = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]
numbers.sort()
print(numbers)  # Output: [1, 1, 2, 3, 3, 4, 5, 5, 5, 6, 9]

# Sorting in reverse order
numbers.sort(reverse=True)
print(numbers)  # Output: [9, 6, 5, 5, 5, 4, 3, 3, 2, 1, 1]

Python Dictionary Methods

1. get()

The get() method returns the value for a given key.

# Example:
person = {'name': 'John', 'age': 30}
print(person.get('name'))  # Output: John
print(person.get('height'))  # Output: None (since height is not a key)
print(person.get('height', 'Unknown'))  # Output: Unknown

2. items()

The items() method returns a view object displaying a list of a dictionary's key-value tuple pairs.

# Example:
person = {'name': 'John', 'age': 30}
for key, value in person.items():
    print(f"{key}: {value}")  # Output: name: John  age: 30

3. keys()

The keys() method returns a view object displaying a list of all keys in the dictionary.

# Example:
person = {'name': 'John', 'age': 30}
print(person.keys())  # Output: dict_keys(['name', 'age'])

4. values()

The values() method returns a view object displaying a list of all values in the dictionary.

# Example:
person = {'name': 'John', 'age': 30}
print(person.values())  # Output: dict_values(['John', 30])

5. update()

The update() method updates the dictionary with the elements from another dictionary object or from an iterable of key-value pairs.