python class behaves like dictionary-or-list-data-like

Question

In python3 console, input those: >>> import sys >>> sys.version_info sys.version_info(major=3, minor=4, micro=3, releaselevel='final', serial=0) >>> type(sys.version_info) # this is class type >>> sys.version_info[0:2] # ?? But it acts like a list-data-like (3, 4) My questions are: How can a class act like dictionary-or-list-data-like? May give an example to construct a class like this? Is there some documentation about this? JavaScript questions and answers, JavaScript questions pdf, JavaScript question bank, JavaScript questions and answers pdf, mcq on JavaScript pdf, JavaScript questions and solutions, JavaScript mcq Test , Interview JavaScript questions, JavaScript Questions for Interview, JavaScript MCQ (Multiple Choice Questions)

Answer 1

Python contains several methods for emulating container types such as dictionaries and lists. In particular, consider the following class: class MyDict(object): def __getitem__(self, key): # Called for getting obj[key] def __setitem__(self, key, value): # Called for setting obj[key] = value If you write obj = MyDict() Then obj[3] will call the first method, and obj[3] = 'foo' will call the second method. If you further want to support len(obj) then you just need to add the method def __len__(self): # Return here the logical length Here is an example of a (very inefficient) dictionary implemented by a list class MyDict(object): def __init__(self, seq=None): self._vals = list(seq) if seq is not None else [] def __getitem__(self, key): return [v[1] for v in self._vals if v[0] == key][0] def __setitem__(self, key, val): self._vals = [v for v in self._vals if v[0] != key] self._vals.append((key, val)) def __len__(self): return len(self._vals) You can use it pretty much like a regular dict: obj = MyDict() obj[2] = 'b' >>> obj[2] 'b'