Object.assign equivalent in python

Is there an equivalent for Javascript's Object.assign(targetDict, srcDict) in python, which takes all the items from one dictionary into another, replacing as we go? (Cleaner than a for-in loop, anyhow)

------ Context ---------

I use Object.assign in javascript to expand out settings-dictionary parameters in large functions, e.g.:

function someFunctionWithLotsOfArguments(namedArg1, namedArg2, namedArg3, namedArg4){}
// turns into
function someFunctionWithLotsOfArguments(argDictionary){
    namedArg1 = argDictionary["namedArg1"]; // etc
}

The first form allows for default arguments while the second one does not, so I then use:

function someFunctionWithLotsOfArguments(namedArg1="default1", namedArg2="default2", namedArg3="default3", namedArg4="default4"){}
// turns into
function someFunctionWithLotsOfArguments(argDictionary){
    defaultArgs = {
        namedArg1: "default1",
        namedArg2: "default2",
        namedArg3: "default3",
        namedArg4: "default4"
    }
    Object.assign(defaultArgs, argDictionary);
    argDictionary = defaultArgs;
    namedArg1 = argDictionary["namedArg1"]; // etc
}

I know, I know, this is a bit of an antipattern, and I should try and group my named arguments into structs to reduce my function parameter count, and if I have a large configurable function with many binary switches I should strip out the common functionality into smaller functions, etc. But if I did need a function like this, is there one available?