درس ۱۴: تابع در پایتون: تابع بازگشتی (Recursive) و Memoization¶

>>> def logger(func):
...     print('Decorator is created!')
...     def func_wrapper(number):
...         print(f'New factorial call with parameter: {number}')
...         result = func(number)
...         print (f'factorial({number}) ==> {result}')
...         return result
...     return func_wrapper
...
>>> @logger
... def factorial(n):
...     if n <= 1:
...         return 1
...     else:
...         return n * factorial(n - 1)
...
>>>
>>> factorial(5)
Decorator is created!
New factorial call with parameter: 5
New factorial call with parameter: 4
New factorial call with parameter: 3
New factorial call with parameter: 2
New factorial call with parameter: 1
factorial(1) ==> 1
factorial(2) ==> 2
factorial(3) ==> 6
factorial(4) ==> 24
factorial(5) ==> 120
120
>>>

>>> import sys

>>> sys.getrecursionlimit()
1000

>>> sys.setrecursionlimit(50)

>>> sys.getrecursionlimit()
50

>>> factorial(9)
362880

>>> sys.setrecursionlimit(10)

>>> factorial(9)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 5, in factorial
  File "<stdin>", line 5, in factorial
  File "<stdin>", line 5, in factorial
  [Previous line repeated 5 more times]
  File "<stdin>", line 2, in factorial
RecursionError: maximum recursion depth exceeded in comparison

>>> def flatten(lists):
...     for sub in lists:
...         if isinstance(sub,list):
...             flatten(sub)
...         else:
...             print(sub)
...
>>> items = [[1,2,3],[4,5,[5,6]],[7,8,9]]
>>> flatten(items)
1
2
3
4
5
5
6
7
8
9
>>>

>>> def genflatten(lists):
...     for sub in lists:
...         if isinstance(sub,list):
...             genflatten(sub)
...         else:
...             yield sub
...
>>> items = [[1,2,3],[4,5,[5,6]],[7,8,9]]

>>> genflatten(items)
<generator object genflatten at 0x7eff06d40150>

>>> list(genflatten(items))
[]

>>> def genflatten(lists):
...     for sub in lists:
...         if isinstance(sub,list):
...             for item in genflatten(sub):
...                 yield item
...         else:
...             yield sub
...
>>> items = [[1,2,3],[4,5,[5,6]],[7,8,9]]

>>> genflatten(items)
<generator object genflatten at 0x7f6cee349258>

>>> list(genflatten(items))
[1, 2, 3, 4, 5, 5, 6, 7, 8, 9]

>>> def fibonacci(n):
...     if n <= 1:
...         return n
...     else:
...         return fibonacci(n-1) + fibonacci(n-2)
...
>>> for number in range(10):
...    print(fibonacci(number))
...
0
1
1
2
3
5
8
13
21
34

>>> def memoize_fibonacci(func):
...     memory = {}
...     def func_wrapper(number):
...         if number not in memory:
...             memory[number] = func(number)
...         return memory[number]
...     return func_wrapper
...
>>> @memoize_fibonacci
... def fibonacci(n):
...     if n <= 1:
...         return n
...     else:
...         return fibonacci(n-1) + fibonacci(n-2)
...
>>>

>>> eval('3*4 + 7.2')
19.2

>>> import math
>>> x = 2
>>> eval('math.sin(3.5+x) + 7.2')
6.494459674429608

eval(object[, globals[, locals]])

>>> globals_env = {'x': 7, 'y': 10, 'birds': ['Parrot', 'Swallow', 'Albatross']}
>>> locals_env = {}
>>> a = eval("3 * x + 4 * y", globals_env, locals_env)
>>> a
61

>>> exec('import math; x=2; print(math.sin(3.5+x) + 7.2)')
6.494459674429608

>>> exec("for i in range(5): print(i)")
0
1
2
3
4

exec(object[, globals[, locals]])

>>> exec("for b in birds: print(b)", globals_env, locals_env)
Parrot
Swallow
Albatross

compile(source, filename, mode, flags=0, dont_inherit=False, optimize=-1)

>>> # compile() with string source

>>> code_str = 'x=5\ny=10\nprint("sum =",x+y)'
>>> code = compile(code_str, 'sum_test.py', 'exec')
>>> print(type(code))
<class 'code'>
>>> exec(code)
sum = 15

>>> # reading code from a file

>>> file = open('/home/saeid/Desktop/test_code.py', 'r')
>>> code_str = file.read()
>>> file.close()
>>> code = compile(code_str, 'test_code.py', 'exec')
>>> print(type(code))
<class 'code'>
>>> exec(code)
Multiplication =  200

>>> a = 0
>>> def func():
...     x = 'text'
...     print('-' * 10)
...     print('locals():')
...     print(locals())
...     print('-' * 10)
...     print('globals():')
...     print(globals())
...
>>> func()
----------
locals():
{'x': 'text'}
----------
globals():
{'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': <class '_frozen_importlib.BuiltinImporter'>, '__spec__': None, '__annotations__': {}, '__builtins__': <module 'builtins' (built-in)>, 'a': 0, 'func': <function func at 0x7f2b29f1ec80>}
>>>

>>> a = 5
>>> b = 10
>>> def func():
...     pass
...
>>> locals()
{'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': <class '_frozen_importlib.BuiltinImporter'>, '__spec__': None, '__annotations__': {}, '__builtins__': <module 'builtins' (built-in)>, 'a': 5, 'b': 10, 'func': <function func at 0x7f1dd0218c80>}
>>> globals()
{'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': <class '_frozen_importlib.BuiltinImporter'>, '__spec__': None, '__annotations__': {}, '__builtins__': <module 'builtins' (built-in)>, 'a': 5, 'b': 10, 'func': <function func at 0x7f1dd0218c80>}
>>>