Creating a list of dictionaries with same keys? [duplicate]

Question

I wanted to create a list that contains x amount of dictionaries all containing the same keys but with different values that's made in a for loop:

Something like

[{'name': Brenda, 'Age': 22, 'Sex': Female},
 {'name': Jorda, 'Age': 32, 'Sex': Male},
 {'name': Richard, 'Age': 54, 'Sex': Male}]

My code is this:

people = []
person = {}

humans = gethumans()

for human in humans:
    number_people, people_data = People.data()
    person['name'] = human.name
    person['age'] = human.age
    person['Sex'] = human.name
    people.append(person)

My output is something like this:

[{'name': Richard, 'Age': 54, 'Sex': Male},
 {'name': Richard, 'Age': 54, 'Sex': Male}
 {'name': Richard, 'Age': 54, 'Sex': Male}]

Since the dictionary values are getting replaced and not added and it's just appending the same dictionary. How can I get around this?

Answer 1

When you append the dictionary person to the list people you are just appending a reference to the dictionary to the list, so the list ends up containing just references to the SAME dictionary.

Since each time through the loop you overwrite the dictionary with new values, at the end the list contains just references to the last person you appended.

What you need to do is create a new dictionary for every person, for example:

for human in humans:
    number_people, people_data = People.data()
    person = dict()
    person['name'] = human.name
    person['age'] = human.age
    person['Sex'] = human.name
    people.append(person)

Answer 2

You each time edit the same dictionary, so you do not construct a new one, but edit the old one. Since you each time append the same dictionary to the list, in the end the list contains the same dictionary n times, and all edits are processed on that dictionary.

You thus have to construct a new dictionary in each iteration in the for loop:

people = []
humans = gethumans()

for human in humans:
    number_people, people_data = People.data()
    person = {
        'name': human.name,
        'age': human.age,
        'sex': human.sex
    }
    people.append(person)

I here replaced 'Sex' with 'sex' (since it is strange to have inconsistent key names), and used human.sex instead of human.name.

Here people.data() do not seem to do anything, you can thus use list comprehension here to generate the list:

people = [
    { 'name': human.name, 'age': human.age, 'sex': human.sex }
    for human in humans
]

This will construct a list with all the dictionaries. Given the for loop had no side-effects (this looks to be the case), the above will work.