Python 優秀代碼編寫
說明
Python慣例
“慣例”這個詞指的是“習慣的做法，常規的辦法，一貫的做法”，與這個詞對應的英文單詞叫“idiom”。由於Python跟其他很多編程語言在語法和使用上還是有比較顯著的差別，因此作為一個Python開發者如果不能掌握這些慣例，就無法寫出“Pythonic”的代碼。下面我們總結了一些在Python開發中的慣用的代碼。
1.讓代碼既可以被導入又可以被執行。
if __name__ == '__main__':2.用下面的方式判斷邏輯“真”或“假”。
if x: if x: if not x:
好
name = 'jackfrued' name = 'jackfrued' fruits = ['apple', 'orange', 'grape'] owners = {'1001': '骆昊', '1002': '王大锤'} if name and fruits and owners: print('I love fruits!') fruits = ['apple', 'orange', 'grape'] name = 'jackfrued' fruits = ['apple', 'orange', 'grape'] owners = {'1001': '骆昊', '1002': '王大锤'} if name and fruits and owners: print('I love fruits!') owners = {'1001': '駱昊', '1002': '王大錘'} name = 'jackfrued' fruits = ['apple', 'orange', 'grape'] owners = {'1001': '骆昊', '1002': '王大锤'} if name and fruits and owners: print('I love fruits!') if name and fruits and owners: 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
name = 'jackfrued' 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!') fruits = ['apple', 'orange', 'grape'] 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!') owners = {'1001': '駱昊', '1002': '王大錘'} 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!') if name != '' and len(fruits) > 0 and owners != {}: 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.善於使用in運算符。
if x in items: # 包含
for x in items: # 迭代好
name = 'Hao LUO' name = 'Hao LUO' if 'L' in name: print('The name has an L in it.') if 'L' in name: name = 'Hao LUO' if 'L' in name: print('The name has an L in it.')
不好
name = 'Hao LUO' name = 'Hao LUO' if name.find('L') != -1: print('This name has an L in it!') if name.find('L') != -1: name = 'Hao LUO' if name.find('L') != -1: print('This name has an L in it!')
4.不使用臨時變量交換兩個值。
a, b = b, a5.用序列構建字符串。
好
chars = ['j', 'a', 'c', 'k', 'f', 'r', 'u', 'e', 'd'] chars = ['j', 'a', 'c', 'k', 'f', 'r', 'u', 'e', 'd'] name = ''.join(chars) print(name) # jackfrued name = ''.join(chars) chars = ['j', 'a', 'c', 'k', 'f', 'r', 'u', 'e', 'd'] name = ''.join(chars) print(name) # jackfrued
不好
chars = ['j', 'a', 'c', 'k', 'f', 'r', 'u', 'e', 'd'] chars = ['j', 'a', 'c', 'k', 'f', 'r', 'u', 'e', 'd'] name = '' for char in chars: name += char print(name) # jackfrued name = '' chars = ['j', 'a', 'c', 'k', 'f', 'r', 'u', 'e', 'd'] name = '' for char in chars: name += char print(name) # jackfrued for char in chars: chars = ['j', 'a', 'c', 'k', 'f', 'r', 'u', 'e', 'd'] name = '' for char in chars: name += char print(name) # jackfrued name += char chars = ['j', 'a', 'c', 'k', 'f', 'r', 'u', 'e', 'd'] name = '' for char in chars: name += char print(name) # jackfrued
6.EAFP優於LBYL。
EAFP -
LBYL -
好
d = {'x': '5'} d = {'x': '5'} try: value = int(d['x']) print(value) except (KeyError, TypeError, ValueError): value = None try: d = {'x': '5'} try: value = int(d['x']) print(value) except (KeyError, TypeError, ValueError): value = None value = int(d['x']) d = {'x': '5'} try: value = int(d['x']) print(value) except (KeyError, TypeError, ValueError): value = None print(value) d = {'x': '5'} try: value = int(d['x']) print(value) except (KeyError, TypeError, ValueError): value = None except (KeyError, TypeError, ValueError): d = {'x': '5'} try: value = int(d['x']) print(value) except (KeyError, TypeError, ValueError): value = None
不好
d = {'x': '5'} 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 if 'x' in d and isinstance(d['x'], str) and d['x'].isdigit(): 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 value = int(d['x']) 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 print(value) 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 else: 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進行迭代。
好
fruits = ['orange', 'grape', 'pitaya', 'blueberry'] fruits = ['orange', 'grape', 'pitaya', 'blueberry'] for index, fruit in enumerate(fruits): print(index, ':', fruit) for index, fruit in enumerate(fruits): fruits = ['orange', 'grape', 'pitaya', 'blueberry'] for index, fruit in enumerate(fruits): print(index, ':', fruit)
不好
fruits = ['orange', 'grape', 'pitaya', 'blueberry'] fruits = ['orange', 'grape', 'pitaya', 'blueberry'] index = 0 for fruit in fruits: print(index, ':', fruit) index += 1 index = 0 fruits = ['orange', 'grape', 'pitaya', 'blueberry'] index = 0 for fruit in fruits: print(index, ':', fruit) index += 1 for fruit in fruits: fruits = ['orange', 'grape', 'pitaya', 'blueberry'] index = 0 for fruit in fruits: print(index, ':', fruit) index += 1 print(index, ':', fruit) 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
data = [7, 20, 3, 15, 11] data = [7, 20, 3, 15, 11] result = [num * 3 for num in data if num > 10] print(result) # [60, 45, 33] result = [num * 3 for num in data if num > 10] data = [7, 20, 3, 15, 11] result = [num * 3 for num in data if num > 10] print(result) # [60, 45, 33]
不好
data = [7, 20, 3, 15, 11] data = [7, 20, 3, 15, 11] result = [] for i in data: if i > 10: result.append(i * 3) print(result) # [60, 45, 33] result = [] data = [7, 20, 3, 15, 11] result = [] for i in data: if i > 10: result.append(i * 3) print(result) # [60, 45, 33] for i in data: data = [7, 20, 3, 15, 11] result = [] for i in data: if i > 10: result.append(i * 3) print(result) # [60, 45, 33] if i > 10: data = [7, 20, 3, 15, 11] result = [] for i in data: if i > 10: result.append(i * 3) print(result) # [60, 45, 33] result.append(i * 3) 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組合鍵和值來創建字典。
好
keys = ['1001', '1002', '1003'] keys = ['1001', '1002', '1003'] values = ['骆昊', '王大锤', '白元芳'] d = dict(zip(keys, values)) print(d) values = ['駱昊', '王大錘', '白元芳'] keys = ['1001', '1002', '1003'] values = ['骆昊', '王大锤', '白元芳'] d = dict(zip(keys, values)) print(d) d = dict(zip(keys, values)) keys = ['1001', '1002', '1003'] values = ['骆昊', '王大锤', '白元芳'] d = dict(zip(keys, values)) print(d)
不好
keys = ['1001', '1002', '1003'] 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) values = ['駱昊', '王大錘', '白元芳'] 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) d = {} 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) for i, key in enumerate(keys): 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) d[key] = values[i] 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)
