## Python惯例 “惯例”这个词指的是“习惯的做法,常规的办法,一贯的做法”,与这个词对应的英文单词叫“idiom”。由于Python跟其他很多编程语言在语法和使用上还是有比较显著的差别,因此作为一个Python开发者如果不能掌握这些惯例,就无法写出“Pythonic”的代码。下面我们总结了一些在Python开发中的惯用的代码。 1. 让代码既可以被导入又可以被执行。 ```Python if __name__ == '__main__': ``` 2. 用下面的方式判断逻辑“真”或“假”。 ```Python if x: if not x: ``` **好**的代码: ```Python name = 'jackfrued' fruits = ['apple', 'orange', 'grape'] owners = {'1001': '骆昊', '1002': '王大锤'} if name and fruits and owners: print('I love fruits!') ``` **不好**的代码: ```Python name = 'jackfrued' fruits = ['apple', 'orange', 'grape'] owners = {'1001': '骆昊', '1002': '王大锤'} if name != '' and len(fruits) > 0 and owners != {}: print('I love fruits!') ``` 3. 善于使用in运算符。 ```Python if x in items: # 包含 for x in items: # 迭代 ``` **好**的代码: ```Python name = 'Hao LUO' if 'L' in name: print('The name has an L in it.') ``` **不好**的代码: ```Python name = 'Hao LUO' if name.find('L') != -1: print('This name has an L in it!') ``` 4. 不使用临时变量交换两个值。 ```Python a, b = b, a ``` 5. 用序列构建字符串。 **好**的代码: ```Python chars = ['j', 'a', 'c', 'k', 'f', 'r', 'u', 'e', 'd'] name = ''.join(chars) print(name) # jackfrued ``` **不好**的代码: ```Python chars = ['j', 'a', 'c', 'k', 'f', 'r', 'u', 'e', 'd'] name = '' for char in chars: name += char print(name) # jackfrued ``` 6. EAFP优于LBYL。 EAFP - **E**asier to **A**sk **F**orgiveness than **P**ermission. LBYL - **L**ook **B**efore **Y**ou **L**eap. **好**的代码: ```Python d = {'x': '5'} try: value = int(d['x']) print(value) except (KeyError, TypeError, ValueError): value = None ``` **不好**的代码: ```Python d = {'x': '5'} if 'x' in d and isinstance(d['x'], str) \ and d['x'].isdigit(): value = int(d['x']) print(value) else: value = None ``` 7. 使用enumerate进行迭代。 **好**的代码: ```Python fruits = ['orange', 'grape', 'pitaya', 'blueberry'] for index, fruit in enumerate(fruits): print(index, ':', fruit) ``` **不好**的代码: ```Python fruits = ['orange', 'grape', 'pitaya', 'blueberry'] index = 0 for fruit in fruits: print(index, ':', fruit) index += 1 ``` 8. 用生成式生成列表。 **好**的代码: ```Python data = [7, 20, 3, 15, 11] result = [num * 3 for num in data if num > 10] print(result) # [60, 45, 33] ``` **不好**的代码: ```Python data = [7, 20, 3, 15, 11] result = [] for i in data: if i > 10: result.append(i * 3) print(result) # [60, 45, 33] ``` 9. 用zip组合键和值来创建字典。 **好**的代码: ```Python keys = ['1001', '1002', '1003'] values = ['骆昊', '王大锤', '白元芳'] d = dict(zip(keys, values)) print(d) ``` **不好**的代码: ```Python keys = ['1001', '1002', '1003'] values = ['骆昊', '王大锤', '白元芳'] d = {} for i, key in enumerate(keys): d[key] = values[i] print(d) ``` > **说明**:这篇文章的内容来自于网络,有兴趣的读者可以阅读[原文](http://safehammad.com/downloads/python-idioms-2014-01-16.pdf)。