How do I go about creating a list of objects (class instances) in Python?
Or is this a result of bad design? I need this cause I have different objects and I need to handle them at a later stage, so I would just keep on adding them to a list and call them later.
Storing a list of object instances is very simple
class MyClass(object):
def __init__(self, number):
self.number = number
my_objects = []
for i in range(100):
my_objects.append(MyClass(i))
# Print the number attribute of each instance
for obj in my_objects:
print(obj.number)
MyClass inherits the properties of an objecti in MyClass (i) refers to the number in the class's __init__ function.You can create a list of objects in one line using a list comprehension.
class MyClass(object): pass
objs = [MyClass() for i in range(10)]
print(objs)
_ for loop variables that aren't referenced in the loop body (i.e. objs = [MyClass() for _ in range(10)])The Python Tutorial discusses how to use lists.
Storing a list of classes is no different than storing any other objects.
def MyClass(object):
pass
my_types = [str, int, float, MyClass]
In Python, the name of the class refers to the class instance. Consider:
class A: pass
class B: pass
class C: pass
lst = [A, B, C]
# instantiate second class
b_instance = lst[1]()
print b_instance
I have some hacky answers that are likely to be terrible... but I have very little experience at this point.
a way:
class myClass():
myInstances = []
def __init__(self, myStr01, myStr02):
self.myStr01 = myStr01
self.myStr02 = myStr02
self.__class__.myInstances.append(self)
myObj01 = myClass("Foo", "Bar")
myObj02 = myClass("FooBar", "Baz")
for thisObj in myClass.myInstances:
print(thisObj.myStr01)
print(thisObj.myStr02)
A hack way to get this done:
import sys
class myClass():
def __init__(self, myStr01, myStr02):
self.myStr01 = myStr01
self.myStr02 = myStr02
myObj01 = myClass("Foo", "Bar")
myObj02 = myClass("FooBar", "Baz")
myInstances = []
myLocals = str(locals()).split("'")
thisStep = 0
for thisLocalsLine in myLocals:
thisStep += 1
if "myClass object at" in thisLocalsLine:
print(thisLocalsLine)
print(myLocals[(thisStep - 2)])
#myInstances.append(myLocals[(thisStep - 2)])
print(myInstances)
myInstances.append(getattr(sys.modules[__name__], myLocals[(thisStep - 2)]))
for thisObj in myInstances:
print(thisObj.myStr01)
print(thisObj.myStr02)
Another more 'clever' hack:
import sys
class myClass():
def __init__(self, myStr01, myStr02):
self.myStr01 = myStr01
self.myStr02 = myStr02
myInstances = []
myClasses = {
"myObj01": ["Foo", "Bar"],
"myObj02": ["FooBar", "Baz"]
}
for thisClass in myClasses.keys():
exec("%s = myClass('%s', '%s')" % (thisClass, myClasses[thisClass][0], myClasses[thisClass][1]))
myInstances.append(getattr(sys.modules[__name__], thisClass))
for thisObj in myInstances:
print(thisObj.myStr01)
print(thisObj.myStr02)
if my_list is the list that you want to store your objects in it and my_object is your object wanted to be stored, use this structure:
my_list.append(my_object)
We have class for students and we want make list of students that each item of list is kind of student
class student :
def __init__(self,name,major):
self.name=name
self.major=major
students = []
count=int(input("enter number of students :"))
#Quantify
for i in range (0,count):
n=input("please enter name :")
m=input("please enter major :")
students.append(student(n,m))
#access
for i in students:
print (i.name,i.major)
I think what you're of doing here is using a structure containing your class instances. I don't know the syntax for naming structures in python, but in perl I could create a structure obj.id[x] where x is an incremented integer. Then, I could just refer back to the specific class instance I needed by referencing the struct numerically. Is this anything in the direction of what you're trying to do?
[type(x), ... ]) or instances of a class ([1, 2, 3])?