Python不是java
Python不是java 同样，php也不是java, 用一种语言的思路来写另一种语言的代码，最后肯定是四不像。 有感。 原文： I was recently looking at the source of a wxPython-based GUI application, about 45.5KLOC in size, not counting the libraries used (e.g. Twisted). The code was written by Java developers who are relatively new to Python, and it suffers from some performance issues (like a 30-second startup time). In examining the code, I found that they had done lots of things that make sense in Java, but which suck terribly in Python. Not because “Python is slower than Java”, but because there are easier ways to accomplish the same goals in Python, that wouldn’t even be possible in Java. So, the sad thing is that these poor folks worked much, much harder than they needed to, in order to produce much more code than they needed to write, that then performs much more slowly than the equivalent idiomatic Python would. Some examples: * A static method in Java does not translate to a Python classmethod. Oh sure, it results in more or less the same effect, but the goal of a classmethod is actually to do something that’s usually not even possible in Java (like inheriting a non-default constructor). The idiomatic translation of a Java static method is usually a module-level function, not a classmethod or staticmethod. (And static final fields should translate to module-level constants.) This isn’t much of a performance issue, but a Python programmer who has to work with Java-idiom code like this will be rather irritated by typing Foo.Foo.someMethod when it should just be Foo.someFunction. But do note that calling a classmethod involves an additional memory allocation that calling a staticmethod or function does not. Oh, and all those Foo.Bar.Baz attribute chains don’t come for free, either. In Java, those dotted names are looked up by the compiler, so at runtime it really doesn’t matter how many of them you have. In Python, the lookups occur at runtime, so each dot counts. (Remember that in Python, “Flat is better than nested”, although it’s more related to “Readability counts” and “Simple is better than complex,” than to being about performance.) * Got a switch statement? The Python translation is a hash table, not a bunch of if-then statments. Got a bunch of if-then’s that wouldn’t be a switch statement in Java because strings are involved? It’s still a hash table. The CPython dictionary implementation uses one of the most highly-tuned hashtable implementations in the known universe. No code that you write yourself is going to work better, unless you’re the genetically-enhanced love child of Guido, Tim Peters, and Raymond Hettinger. ...