Functional Python: 4th version

docs/functional_python.md

@@ -77,6 +77,25 @@
 
 ---
 
+### Lambdas
+
+- anonymous functions
+- not fully true in Python
+    - it's basically just an expression
+
+---
+
+### Lambdas
+
+```python
+(lambda x,y:x+y)(1, 2)
+
+foo=lambda x,y:x+y
+foo(1,2)
+```
+
+---
+
 ### Higher order functions
 
 - must exist by definition
@@ -87,27 +106,111 @@
 
 ---
 
+#### Higher order functions
+
+```python
+def foo():
+    def bar():
+        print("BAR")
+    return bar
+
+x = foo()
+x()
+```
+
+---
+
+#### Higher order functions
+
+```python
+def add(x, y):
+    return x + y
+
+
+def mul(x, y):
+    return x * y
+
+
+def less_than(x, y):
+    return x < y
+
+
+def get_operator(symbol):
+    operators = {
+            "+": add,
+            "*": mul,
+            "<": less_than,
+    }
+    return operators[symbol]
+
+
+def calc(operator, x, y):
+    return operator(x, y)
+
+
+z = calc(get_operator("+"), 10, 20)
+print(z)
+
+z = calc(get_operator("*"), 10, 20)
+print(z)
+
+z = calc(get_operator("<"), 10, 20)
+print(z)
+```
+
+---
+
 #### `map`
 
+```python
+values = range(-10, 11)
+
+converted = map(abs, values)
+print(list(converted))
+```
+
 ---
 
 #### `filter`
 
+```python
+message = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua"
+words = message.split()
+
+filtered = filter(lambda word: len(word) > 4, words)
+print(list(filtered))
+```
+
 ---
 
 #### `reduce`
 
----
+```python
+from functools import reduce
 
-### Lambdas
 
-- anonymous functions
-- not fully true in Python
-    - it's basically just an expression
+def multiply(x, y):
+    return x * y
+
+
+x = range(1, 11)
+print(x)
+
+y = reduce(multiply, x)
+print(y)
+```
 
 ---
 
-#### Lambdas
+### Factorial computation
+
+```python
+n = range(0, 11)
+
+factorials = map(lambda n: reduce(lambda a, b: a*b, range(1, n+1), 1), n)
+
+print(list(factorials))
+```
 
 ---
 
@@ -124,9 +227,50 @@
 
 #### Counter (incorrect)
 
+```python
+def createCounter():
+    counter = 0
+    def next():
+        counter += 1
+        return counter
+    return next
+
+counter1 = createCounter()
+counter2 = createCounter()
+for i in range(1,11):
+    result1 = counter1()
+    result2 = counter2()
+    print("Iteration #%d" % i)
+    print("    Counter1: %d" % result1)
+    print("    Counter2: %d" % result2)
+```
+
+---
+
+#### Counter (correct for Python 2.x)
+
+```python
+def createCounter():
+    counter = [0]
+    def next():
+        counter[0] += 1
+        return counter[0]
+    return next
+```
+
 ---
 
-#### Counter (correct)
+#### Counter (correct for Python 3.x)
+
+```python
+def createCounter():
+    counter = 0
+    def next():
+        nonlocal counter
+        counter += 1
+        return counter
+    return next
+```
 
 ---
 
@@ -142,18 +286,34 @@
 
 #### Tuple comprehension
 
+```python
+```
+
 ---
 
 #### List comprehension
 
+```python
+message = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua"
+words = message.split()
+
+lengths = [len(word) for word in words]
+```
+
 ---
 
 #### Set comprehension
 
+```python
+```
+
 ---
 
 #### Dict comprehension
 
+```python
+```
+
 ---
 
 ### Partial functions
@@ -162,10 +322,44 @@
 
 #### `partial` usage
 
+```python
+from functools import partial
+
+
+def mul(x, y):
+    return x * y
+
+
+print(mul(6, 7))
+
+print()
+
+doubler = partial(mul, 2)
+
+
+for i in range(11):
+    print(i, doubler(i))
+```
+
 ---
 
 ### `partialmethod` usage
 
+```python
+class Foo:
+    def __init__(self):
+        self._enabled = False
+
+    def set_enabled(self, state):
+        self._enabled = state
+
+    enable = partialmethod(set_enabled, True)
+    disable = partialmethod(set_enabled, False)
+
+    def __str__(self):
+        return "Foo that is " + ("enabled" if self._enabled else "disabled")
+```
+
 ---
 
 ### Caching
@@ -178,3 +372,77 @@
 ---
 
 #### `lru_cache` usage
+
+```python
+from time import time
+from functools import lru_cache
+
+@lru_cache
+def fib(n):
+    if n < 2:
+        return n
+    return fib(n-1) + fib(n-2)
+
+
+max_n = 300
+
+for _ in range(10):
+    start = time()
+    result = fib(max_n)
+    end = time()
+    print(result, end - start)
+```
+
+---
+
+#### `lru_cache` usage #2
+
+```python
+from time import time
+from functools import lru_cache
+
+@lru_cache
+def fib(n):
+    if n < 2:
+        return n
+    return fib(n-1) + fib(n-2)
+
+
+max_n = 300
+
+for i in range(20):
+    if i % 5 == 0:
+        fib.cache_clear()
+    print(fib.cache_info())
+    start = time()
+    result = fib(max_n)
+    end = time()
+    print(result, end - start)
+```
+
+---
+
+#### `cache` usage
+
+```python
+from time import time
+from functools import cache
+
+@cache
+def fib(n):
+    if n < 2:
+        return n
+    return fib(n-1) + fib(n-2)
+
+
+max_n = 300
+
+for i in range(20):
+    if i % 5 == 0:
+        fib.cache_clear()
+    print(fib.cache_info())
+    start = time()
+    result = fib(max_n)
+    end = time()
+    print(result, end - start)
+```