Python provides a rich set of built-in functions that can be used directly without importing any libraries. Below are some commonly used built-in functions along with brief descriptions and examples.

1. Mathematical Funtcions

# Returns absolute value
>>> abs(-5)
5

# Returns the power; if third argument is given, returns remainder after division
>>> pow(2, 4)
16
>>> pow(2, 3, 10)
8

# divmod() returns quotient and remainder
>>> divmod(123, 10)
(12, 3)
>>> divmod(123, 5)
(24, 3)

# Rounds a number to nearest integer
>>> round(2.5)
2
>>> round(2.6)
3

# max() and min() return the maximum and minimum of a sequence

2. Type Conversion Functions

# str() converts other types to string
# list() and tuple() convert other iterables to list and tuple

# int() converts to integer
>>> int(1.5)
1
>>> int(1.9)
1

# float() converts to float
>>> float(1.3)
1.3
>>> float(1)
1.0

3. Sequence and Iteration Related Functions

# len() returns the length of an object

# reversed() returns a reverse iterator; can be applied to lists, tuples, strings, etc.
for i in reversed([1, 3, 2]):
    print(i)
# output:
2
3
1

# Reverse in-place using .reverse() method
>>> my_list = [1, 3, 2]
>>> my_list.reverse()
>>> my_list
[2, 3, 1]

# slice() returns a slice object: slice(start, stop, step)
s = slice(2, 5)
my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9]
result = my_list[s]  # [3, 4, 5]

# zip() pairs elements from multiple iterators into a list of tuples
for item in zip([1, 2, 3], ['a', 'b', 'c']):
    print(item)
(1, 'a')
(2, 'b')
(3, 'c')

# map() applies a function to every item of an iterable
def square(n):
    return n ** 2

for num in map(square, [1, 2, 3, 4]):
    print(num)
# 1
# 4
# 9
# 16

# filter() filters elements based on a function
def is_odd(x):
    return x % 2 == 1

for num in filter(is_odd, [1, 2, 3, 4]):
    print(num)
# 1
# 3

# sorted() returns a new sorted list from an iterable; can also take a key function
my_list = [1, 3, 2, 4]
sorted(my_list)  # [1, 2, 3, 4]

# .sort() sorts the list in-place
my_list.sort()
my_list  # [1, 2, 3, 4]

# reduce() from functools; applies a function cumulatively
from functools import reduce

def add(x, y):
    return x + y

numbers = [1, 2, 3, 4, 5]
result = reduce(add, numbers)
print(result)  # 15

4. Logical and Comparison Functions

# any() returns True if any element of the iterable is truthy
>>> any([1, 3, 2, 0])
True
>>> any([])
False
>>> any([[]])
False
>>> any([[], 1])
True

# all() returns True if all elements of the iterable are truthy
>>> all([1, 3, 2, 0])
False
>>> all([])
True
>>> all([[], 1])
False

5. String Processing Functions

# ascii() returns a string containing a printable representation of an object
>>> ascii('1')
"'1'"
>>> ascii(1)
'1'
>>> ascii('a')
"'a'"

# repr() returns a string representation of an object
>>> repr(1)
'1'
>>> repr('1')
"'1'"

# ord() returns the Unicode code point of a character; chr() returns the character from a code point
>>> ord('1')
49
>>> ord('a')
97
>>> chr(1)
'\x01'
>>> chr('a')  # Error: string cannot be interpreted as integer
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'str' object cannot be interpreted as an integer

6. Base Conversion Functions

# bin() converts to binary string
>>> bin(10)
'0b1010'

# oct() converts to octal string
>>> oct(10)
'0o12'

# hex() converts to hexadecimal string
>>> hex(10)
'0xa'

7. Other Utility Functoins

# print() outputs text
# format() formats strings and numbers

>>> print(format("test", "^20"))  # center alignment
       test
>>> print(format("test", "<20"))  # left alignment
test               
>>> print(format("test", ">20"))  # right alignment
               test

# Format specifiers for numbers:
print(format(3, "b"))  # binary: 11
print(format(97, "c"))  # Unicode character: a
print(format(11, "d"))  # decimal: 11
print(format(11, "o"))  # octal: 13
print(format(11, "x"))  # hexadecimal lowercase: b
print(format(11, "X"))  # hexadecimal uppercase: B
print(format(11, "n"))  # same as d: 11
print(format(11))       # same as d: 11
print(format(123456789, "e"))  # scientific notation, 6 decimal places: 1.234568e+08
print(format(123456789, "0.2e"))  # scientific notation, 2 decimal places: 1.23e+08
print(format(123456789, "0.2E"))  # scientific notation, 2 decimal places (uppercase): 1.23E+08
print(format(1.23456789, "f"))  # fixed-point, 6 decimal places: 1.234568
print(format(1.23456789, "0.2f"))  # fixed-point, 2 decimal places: 1.23
print(format(1.23456789, "0.10f"))  # fixed-point, 10 decimal places: 1.2345678900
print(format(1.23456789e+3, "F"))  # fixed-point, large numbers output INF: 1234.567890

# input() gets user input
# range() generates a sequence of integers