Suppose you have to create 10 class objects in python, and do something with them, like:
obj_1 = MyClass()
other_object.add(obj_1)
obj_2 = MyClass()
other_object.add(obj_2)
.
.
.
obj_10 = MyClass()
other_object.add(obj_10)
How would you do it with a loop, and assign a variable to each object (like obj_1), so that the code will be shorter? Each object should be accessible outside the loop
obj_1.do_sth()
This question is asked every day in some variation. The answer is: keep your data out of your variable names, and this is the obligatory blog post.
In this case, why not make a list of objs?
objs = [MyClass() for i in range(10)]
for obj in objs:
other_object.add(obj)
objs[0].do_sth()
you can use list to define it.
objs = list()
for i in range(10):
objs.append(MyClass())
Creating a dictionary as it has mentioned, but in this case each key has the name of the object name that you want to create. Then the value is set as the class you want to instantiate, see for example:
class MyClass:
def __init__(self, name):
self.name = name
self.checkme = 'awesome {}'.format(self.name)
...
instanceNames = ['red', 'green', 'blue']
# Here you use the dictionary
holder = {name: MyClass(name=name) for name in instanceNames}
Then you just call the holder key and you will have all the properties and methods of your class available for you.
holder['red'].checkme
output:
'awesome red'
Using a dictionary for unique names without a name list:
class MyClass:
def __init__(self, name):
self.name = name
self.pretty_print_name()
def pretty_print_name(self):
print("This object's name is {}.".format(self.name))
my_objects = {}
for i in range(1,11):
name = 'obj_{}'.format(i)
my_objects[name] = my_objects.get(name, MyClass(name = name))
Output:
"This object's name is obj_1."
"This object's name is obj_2."
"This object's name is obj_3."
"This object's name is obj_4."
"This object's name is obj_5."
"This object's name is obj_6."
"This object's name is obj_7."
"This object's name is obj_8."
"This object's name is obj_9."
"This object's name is obj_10."
I hope this is what you are looking for.
class Try:
def do_somthing(self):
print 'Hello'
if __name__ == '__main__':
obj_list = []
for obj in range(10):
obj = Try()
obj_list.append(obj)
obj_list[0].do_somthing()
Output:
Hello
Hi there here is the answer I think they wanted below:
class Neuron:
def __init__(self, name):
self.name = name
Neurons=[]
for x in range(6):
Neurons.append(Neuron(x))
for x in Neurons:
print(x.name)
print(Neurons)
This solution helps to create several instances of a class using a for loop as well as the globals() function.
class Cir:
def __init__(self, name):
self.name = name
This code defines a class called Cir with an __init__ method that takes a single argument name and assigns it to the object's name attribute.
for i in range(5):
inst_name = "my_instance_" + str(i)
globals()[inst_name] = Cir(inst_name)
This loop creates five instances of the Cir class and assigns them to global variables with names that depend on the value of the loop variable i. The variable inst_name is created as a string that adds the constant string my_instance_ with the string representation of the loop variable i. Then, the globals() function returns a dictionary of the global symbol table, and the resulting dictionary is accessed using inst_name as a key to add a new global variable with the name specified in inst_name and the value of the newly created instance of the Cir class with the name attribute set to inst_name.
print(my_instance_3.name)
This line of code prints the name attribute of the my_instance_3 and ensures that the instances were created properly.
I did so, but the IDE indicates an error. You can experiment. eval() and exec() create vulnerable code sections.
class LinkedList:
def __init__(self, value, next=None):
self.value = value
self.next = next
for i in range(1, 11):
exec(f'linked_{i} = LinkedList({i})')
if i > 1:
exec(f'linked_{i - 1}.next = linked_{i}')
print(linked_1) # <__main__.LinkedList object at 0x00000258AF6E3B80>
