按扩展名定类型

一张扩展名到类型的表。看几个文件各配什么类型，没登记的一律 application/octet-stream：

TYPES = {".css": "text/css", ".js": "application/javascript", ".png": "image/png", ".html": "text/html", ".json": "application/json"}

def ctype(name):
    dot = name.rfind(".")
    return TYPES.get(name[dot:] if dot >= 0 else "", "application/octet-stream")

print(",".join(ctype(n) for n in ("style.css", "app.js", "logo.png", "README", "data.json")))