How to create a list of objects?
Question:
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.
Answers:
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]
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))
# later
for obj in my_objects:
print obj.number
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?
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
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)
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)
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)
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)
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.
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]
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))
# later
for obj in my_objects:
print obj.number
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?
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
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)
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)
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)
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)