rspec/rules/S4143/python/rule.adoc

It is highly suspicious when a value is saved in a collection for a given key or index and then unconditionally overwritten. Such replacements are likely errors.

This rule raises an issue when the https://docs.python.org/3/reference/datamodel.html#object.__setitem__[``++__setitem__++``] method of the same object is called multiple times with the same index, slice or key without any other action done between the calls.

== Noncompliant Code Example

----
def swap(mylist, index1, index2):
    tmp = mylist[index2]
    mylist[index2] = mylist[index1]
    mylist[index2] = tmp  # Noncompliant

list2 = [0,1,2,3,4,5,6,7,8,9]
list2[3:5] = [42,42]
list2[3:5] = [42,42]  # Noncompliant

mymap = {'a': {}}
mymap['a']['b'] = 42
mymap['a']['b'] = 42  # Noncompliant
----