1. sorted()
Description: Returns a new sorted list from the items in iterable.
python
# 1. Sort list of numbers
numbers = [3, 1, 4, 1, 5, 9, 2]
print(sorted(numbers)) # [1, 1, 2, 3, 4, 5, 9]
# 2. Sort list of strings
fruits = ["banana", "apple", "cherry"]
print(sorted(fruits)) # ['apple', 'banana', 'cherry']
# 3. Reverse sort
print(sorted(numbers, reverse=True)) # [9, 5, 4, 3, 2, 1, 1]
# 4. Sort tuple
tup = (5, 2, 8, 1)
print(sorted(tup)) # [1, 2, 5, 8]
# 5. Sort string (returns list of characters)
word = "python"
print(sorted(word)) # ['h', 'n', 'o', 'p', 't', 'y']
# 6. Sort by key (string length)
words = ["cat", "elephant", "dog"]
print(sorted(words, key=len)) # ['cat', 'dog', 'elephant']
# 7. Sort by absolute value
numbers = [-5, 3, -1, 4, -2]
print(sorted(numbers, key=abs)) # [-1, -2, 3, 4, -5]
# 8. Sort dictionary keys
d = {"b": 2, "a": 1, "c": 3}
print(sorted(d)) # ['a', 'b', 'c']
# 9. Sort with custom key (last character)
words = ["apple", "banana", "cherry"]
print(sorted(words, key=lambda x: x[-1])) # ['banana', 'apple', 'cherry']
# 10. Sort mixed types (raises error)
mixed = [1, "a", 2]
# sorted(mixed) would raise TypeError
2. reversed()
Description: Returns a reverse iterator.
python
# 1. Reverse list
lst = [1, 2, 3, 4]
print(list(reversed(lst))) # [4, 3, 2, 1]
# 2. Reverse string
s = "hello"
print(''.join(reversed(s))) # 'olleh'
# 3. Reverse tuple
tup = (1, 2, 3)
print(tuple(reversed(tup))) # (3, 2, 1)
# 4. Reverse range
r = range(5)
print(list(reversed(r))) # [4, 3, 2, 1, 0]
# 5. Use in for loop
for num in reversed([1, 2, 3]):
print(num) # 3, 2, 1
# 6. Reverse and convert to list
numbers = [5, 2, 8, 1]
reversed_list = list(reversed(numbers))
print(reversed_list) # [1, 8, 2, 5]
# 7. Reverse string characters
word = "python"
reversed_chars = list(reversed(word))
print(reversed_chars) # ['n', 'o', 'h', 't', 'y', 'p']
# 8. Reverse bytes
b = bytes([1, 2, 3])
print(bytes(reversed(b))) # b'\x03\x02\x01'
# 9. Multiple reversals
lst = [1, 2, 3]
rev1 = list(reversed(lst))
rev2 = list(reversed(rev1))
print(rev2) # [1, 2, 3]
# 10. Reverse empty iterable
print(list(reversed([]))) # []
3. slice()
Description: Returns a slice object for slicing sequences.
python
# 1. Basic slicing lst = [0, 1, 2, 3, 4, 5] s = slice(2, 5) print(lst[s]) # [2, 3, 4] # 2. Slice with step s = slice(1, 6, 2) print(lst[s]) # [1, 3, 5] # 3. Slice from start s = slice(3) print(lst[s]) # [0, 1, 2] # 4. Slice to end s = slice(2, None) print(lst[s]) # [2, 3, 4, 5] # 5. Negative slicing s = slice(-3, -1) print(lst[s]) # [3, 4] # 6. Slice string text = "hello world" s = slice(6, 11) print(text[s]) # 'world' # 7. Slice with all parameters s = slice(1, 8, 3) numbers = list(range(10)) print(numbers[s]) # [1, 4, 7] # 8. Slice tuple tup = (0, 1, 2, 3, 4, 5) s = slice(1, 4) print(tup[s]) # (1, 2, 3) # 9. Reuse slice object s = slice(0, 3) lst1 = [1, 2, 3, 4, 5] lst2 = [10, 20, 30, 40, 50] print(lst1[s], lst2[s]) # [1, 2, 3] [10, 20, 30] # 10. Slice with None values s = slice(None, None, 2) print(lst[s]) # [0, 2, 4]
4. iter()
Description: Returns an iterator object.
python
# 1. Create iterator from list
lst = [1, 2, 3]
it = iter(lst)
print(next(it)) # 1
print(next(it)) # 2
print(next(it)) # 3
# 2. Iterator from string
s = "hi"
it = iter(s)
print(list(it)) # ['h', 'i']
# 3. Iterator from tuple
tup = (1, 2, 3)
it = iter(tup)
print(next(it)) # 1
# 4. Iterator from range
r = range(3)
it = iter(r)
print(list(it)) # [0, 1, 2]
# 5. Use in for loop (implicit)
it = iter([1, 2, 3])
for item in it:
print(item) # 1, 2, 3
# 6. Iterator from dictionary keys
d = {"a": 1, "b": 2}
it = iter(d)
print(list(it)) # ['a', 'b']
# 7. Iterator from set
my_set = {1, 2, 3}
it = iter(my_set)
print(next(it)) # 1 (order may vary)
# 8. Exhausted iterator
it = iter([1, 2])
print(next(it)) # 1
print(next(it)) # 2
# next(it) would raise StopIteration
# 9. Iterator from bytes
b = bytes([65, 66, 67])
it = iter(b)
print(bytes(it)) # b'ABC'
# 10. Multiple iterators from same list
lst = [1, 2, 3]
it1 = iter(lst)
it2 = iter(lst)
print(next(it1), next(it2)) # 1, 1
Bonus: Combined Examples
python
# Combined: sorted + reversed numbers = [3, 1, 4, 1, 5] sorted_reversed = list(reversed(sorted(numbers))) print(sorted_reversed) # [5, 4, 3, 1, 1] # Combined: slice + sorted lst = [5, 2, 8, 1, 9, 3] s = slice(1, 5, 2) sorted_slice = sorted(lst)[s] print(sorted_slice) # [2, 5] # Combined: iter + slice numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] s = slice(2, 8, 2) it = iter(numbers[s]) print(list(it)) # [2, 4, 6] # Combined: all functions data = [9, 1, 5, 3, 7, 2, 8, 4, 6] # Sort, reverse, take slice, create iterator result = iter(reversed(sorted(data))[2:6]) print(list(result)) # [7, 6, 5, 4]
These functions are essential for working with sequences and iterables in Python, providing powerful ways to manipulate and traverse data!