python array data structure

Question

is there a data structure in python that is equivalent to array in cpp? one that some elements are initialized and some are not? for example, in python list: [1,2,3], elements have to be sequentially filled in cpp array can be a[0] == 0, a1 -- arbitrary, uninitialized, a[2] == 2

is there an cpp-array equivalent structure in python? ps, python array doesn't seem to be equivalent, all elements have to be filled sequentially too

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• Adrian Shum: By what way it is not "equivalent"? Just because you cannot leave garbage in certain element of list?

Answer 1

Perhaps this answer here on StackOverflow may be what you are looking for?

How to create a fix size list in python?

Answer 2

You can probably put together some kind of wrapper using a dictionary:

class CppArray:
 def __init__(self, value):
 if value == None:
 self.data = {}
 self.length = 0
 else:
 self.data = { 0: value }
 self.length = 1
 def insert(self, index, value):
 while index in self.data:
 tmp = self.data[index]
 self.data[index] = value
 value = tmp
 index = index + 1
 self.data[index] = value
 if index >= self.length:
 self.length = index + 1
 def __getitem__(self, index):
 if (index < 0 or index >= self.length):
 # must create IndexException
 raise IndexException("Index out of range")
 if index in self.data:
 return self.data[index]
 else:
 return None
x = CppArray("i")
x.insert(0,10)
x.insert(200,30)
x[1]

Obviously this quick sketch is missing many details which would make the class more useful.

For other ideas on special methods you could use, check:

https://docs.python.org/3/reference/datamodel.html