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Refactoring Legacy Code

MediumCoding00:00
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Your question is Refactoring Legacy Code. Take a moment with it on the right.

Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).

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Problem

CI Financial's reporting team maintains a legacy script that formats client portfolio statements before they go out each quarter. The function below has been patched by several people over the years and nobody wants to touch it anymore.

def gen_rpt(d, t, f):
    r = ""
    for x in d:
        if t == 1:
            r = r + x["nm"] + ": " + str(x["v"]) + "
"
        elif t == 2:
            if x["v"] > 0:
                r = r + x["nm"] + ": +" + str(x["v"]) + "
"
            else:
                r = r + x["nm"] + ": " + str(x["v"]) + "
"
        else:
            r = r + x["nm"] + "
"
    if f == "usd":
        r = r.replace("v", "USD")
    return r

It's called once per client per quarter to build the plain-text section of a portfolio statement. Explain what you would change about this function to make it maintainable by someone other than its original author, and why.