When creating a new pair in a dictionary lose the previous data?

Question

I’m creating a Dict from scratch, but when I add some new pair, the old pair gets lost. If I try to print 'name' for example, it gives error.

cidade = {
    'nome': 'São Paulo',
    'estado': 'São Paulo'
}

print(cidade)    
print(cidade['nome'])    
cidade = {'país': 'Brasil'}    
#print(cidade['nome'])    
print(cidade)

Take the penultimate comment print() that you will see the mistake happening.

Answer 1

You are not creating a new key and value pair, you are creating a new dictionary and saving in it variable, so its previous value is lost, since it cannot store two different values in the same variable.

If you want to add a new element you should create it through the standard dictionary syntax saying that you have a key that did not exist before and storing a value in the key and not in the dictionary. The key is like a different variable, that is, the dictionary is an object full of variables.

Another way is to use a method that the dictionary object has by default and it changes the object for you. Documentation.

cidade = {
    'nome': 'São Paulo',
    'estado': 'São Paulo'
}
cidade['país'] = 'Brasil'
cidade.update({'cep': '01000'})
print(cidade)

Behold working in the ideone. And in the repl it.. Also put on the Github for future reference.