{"id":7032,"date":"2005-05-16T00:00:00","date_gmt":"2005-05-15T14:00:00","guid":{"rendered":"http:\/\/michael.ellerman.id.au\/blog\/2005\/05\/16\/real-work-with-python\/"},"modified":"2007-10-25T13:56:01","modified_gmt":"2007-10-25T03:56:01","slug":"real-work-with-python","status":"publish","type":"post","link":"https:\/\/michael.ellerman.id.au\/blog\/2005\/05\/16\/real-work-with-python\/","title":{"rendered":"“Real work” with Python"},"content":{"rendered":"

I just stumbled across Benjamin Carlyle’s<\/a> piece titled Hungarian Notation Revisited<\/a>. He’s replying to a reply to a blah blah of an article by Joel<\/a> on (among other things) differentiating “safe” and “unsafe” strings in web apps.<\/p>\n

I absolutely agree with his point that Hungarian notation is broken because it asks the programmer to do the compiler’s job. I also think it makes code much harder<\/strong> to read, because you’re constantly tripping over details that are (usually) irrelevant to the underlying algorithm.<\/p>\n

He goes on to suggest that Python isn’t suitable for “real work” because of its “lack of ability to state the expectations of a particular function”. His premise is<\/strong> wrong, and I also believe his conclusion is wrong, but I leave that as matter of religion<\/strike> opinion.<\/p>\n

Strict typing in Python is not the default, but it is painless:<\/p>\n

\r\nclass<\/strong> SafeString(<\/span>str<\/span>):<\/span>\r\n    def<\/strong> __init__(<\/span>self<\/span>, value):<\/span>\r\n        # check value is 'safe' here, then call super class constructor<\/em><\/span>\r\n        str<\/span>.__init__(<\/span>self<\/span>, value)<\/span>\r\n\r\ndef<\/strong> only_print_safe_string(<\/span>s):<\/span>\r\n    assert<\/strong> isinstance<\/span>(<\/span>s, SafeString)<\/span>\r\n    print<\/strong> s\r\n\r\ns =<\/span> SafeString(<\/span>'This is a safe string'<\/span>)<\/span>\r\n\r\nonly_print_safe_string(<\/span>s)<\/span>\r\nonly_print_safe_string(<\/span>'This will not get printed'<\/span>)<\/span><\/pre>\n
Coming from C or C++ that probably seems a bit weird. “I have to add an assertion just to get type checking?”<\/p>\n
But if you think about it, in a dynamic language, that’s all type checking is, an assertion at the function entry point. Python gives you the flexibility to do it when you need to, but only then.<\/p>\n
I just stumbled across Benjamin Carlyle’s piece titled Hungarian Notation Revisited. He’s replying to a reply to a blah blah of an article by Joel on (among other things) differentiating “safe” and “unsafe” strings in web apps. I absolutely agree with his point that Hungarian notation is broken because it asks the programmer to do […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[12],"tags":[28],"_links":{"self":[{"href":"https:\/\/michael.ellerman.id.au\/blog\/wp-json\/wp\/v2\/posts\/7032"}],"collection":[{"href":"https:\/\/michael.ellerman.id.au\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/michael.ellerman.id.au\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/michael.ellerman.id.au\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/michael.ellerman.id.au\/blog\/wp-json\/wp\/v2\/comments?post=7032"}],"version-history":[{"count":0,"href":"https:\/\/michael.ellerman.id.au\/blog\/wp-json\/wp\/v2\/posts\/7032\/revisions"}],"wp:attachment":[{"href":"https:\/\/michael.ellerman.id.au\/blog\/wp-json\/wp\/v2\/media?parent=7032"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/michael.ellerman.id.au\/blog\/wp-json\/wp\/v2\/categories?post=7032"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/michael.ellerman.id.au\/blog\/wp-json\/wp\/v2\/tags?post=7032"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
I would also argue that strict typing on its own, is rarely enough to do proper Design by Contract<\/a>. In most cases the prerequisites for a function can not be expressed simply by the types of the arguments, you need to assert something about their values<\/em>. And in those cases, even in C and C++, what you end up with is assert.<\/p>\n","protected":false},"excerpt":{"rendered":"