Python data hiding All In One

Python data hiding All In One

private data / private method

⚠️ 约定：class 里面使用单个下划线，表示私有的属性或私有的方法，实际上在 class 外面是可以访问的

def _private_method():
  self._private_data = ""

Strongly private methods and attributes have a double underscore at the beginning of their names.
This causes their names to be mangled, which means that they can't be accessed from outside the class.

class Spam:
  __egg = 7
  def print_egg(self):
    print(self.__egg)

s = Spam()
s.print_egg()
# instance._Class__attribute 🚀
print("✅ s._Spam__egg =", s._Spam__egg)
# print("❓ s._Spam =", s._Spam)
# ❌ AttributeError: 'Spam' object has no attribute '_Spam'
print(s.__egg)


"""
$ py3 ./data-hiding-strong-private.py

7
✅ s._Spam__egg = 7
Traceback (most recent call last):
  File "/Users/xgqfrms-mm/Documents/github/Python-3.x-All-In-One/src/./data-hiding-strong-private.py", line 9, in <module>
    print(s.__egg)
AttributeError: 'Spam' object has no attribute '__egg'
"""

demos

class Queue:
  def __init__(self, contents):
    self._hidden_list = list(contents)

  def push(self, value):
    self._hidden_list.insert(0, value)

  def pop(self):
    return self._hidden_list.pop(-1)

  def __repr__(self):
    return "Queue({})".format(self._hidden_list)

queue = Queue([1, 2, 3])
print(queue)
queue.push(0)
print(queue)
queue.pop()
print(queue)
print(queue._hidden_list)


"""

$ py3 ./data-hiding-queue.py

Queue([1, 2, 3])
Queue([0, 1, 2, 3])
Queue([0, 1, 2])
[0, 1, 2]
"""

class Spam:
  __egg = 7
  def print_egg(self):
    print(self.__egg)

s = Spam()
s.print_egg()
# instance._Class__attribute 🚀
print("✅ s._Spam__egg =", s._Spam__egg)

# 如何访问 python class 的属性
print("✅ Spam._Spam__egg =", Spam._Spam__egg)
# print("❓ s._Spam =", s._Spam)
# ❌ AttributeError: 'Spam' object has no attribute '_Spam'

# print(s.__egg)

"""
$ py3 ./data-hiding-strong-private.py

7
✅ s._Spam__egg = 7
✅ Spam._Spam__egg = 7
Traceback (most recent call last):
  File "/Users/xgqfrms-mm/Documents/github/Python-3.x-All-In-One/src/./data-hiding-strong-private.py", line 9, in <module>
    print(s.__egg)
AttributeError: 'Spam' object has no attribute '__egg'
"""

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refs

https://www.cnblogs.com/xgqfrms/p/17565339.html

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