Python由於語言的簡潔性，讓我們以人類思考的方式來寫代碼，新手更容易上手，老鳥更愛不釋手。
要寫出 Pythonic（優雅的、地道的、整潔的）代碼，還要平時多觀察那些大牛代碼，Github 上有很多非常優秀的源代碼值得閱讀，比如：requests、flask、tornado，這裏收集了一些常見的 Pythonic 寫法，幫助你養成寫優秀代碼的習慣。
變量交換
- Bad
tmp = a a = b b = tmp
- Pythonic
a,b = b,a
列表推導
- Bad
my_list = [] for i in range(10): my_list.append(i*2)
- Pythonic
my_list = [i*2 for i in range(10)]
單行表達式
- 雖然列表推導式由於其簡潔性及表達性，被廣受推崇。
- 但是有許多可以寫成單行的表達式，並不是好的做法。
- Bad
print 'one'; print 'two' if x == 1: print 'one' if <complex comparison> and <other complex comparison>: # do something
- Pythonic
print 'one' print 'two' if x == 1: print 'one' cond1 = <complex comparison> cond2 = <other complex comparison> if cond1 and cond2: # do something
帶索引遍歷
- Bad
for i in range(len(my_list)): print(i, "-->", my_list[i])
- Pythonic
for i,item in enumerate(my_list): print(i, "-->",item)
序列解包
- Pythonic
a, *rest = [1, 2, 3] # a = 1, rest = [2, 3] a, *middle, c = [1, 2, 3, 4] # a = 1, middle = [2, 3], c = 4 1
字符串拼接
- Bad
letters = ['s', 'p', 'a', 'm'] s="" for let in letters: s += let
- Pythonic
letters = ['s', 'p', 'a', 'm'] word = ''.join(letters)
真假判斷
- Bad
if attr == True: print 'True!' if attr == None: print 'attr is None!'
- Pythonic
if attr: print 'attr is truthy!' if not attr: print 'attr is falsey!' if attr is None: print 'attr is None!'
訪問字典元素
- Bad
d = {'hello': 'world'}
if d.has_key('hello'):
print d['hello'] # prints 'world'
else:
print 'default_value'
- Pythonic
d = {'hello': 'world'}
print d.get('hello', 'default_value') # prints 'world'
print d.get('thingy', 'default_value') # prints 'default_value'
# Or:
if 'hello' in d:
print d['hello']
操作列表
- Bad
a = [3, 4, 5] b = [] for i in a: if i > 4: b.append(i)
- Pythonic
a = [3, 4, 5] b = [i for i in a if i > 4] # Or: b = filter(lambda x: x > 4, a)
- Bad
a = [3, 4, 5] for i in range(len(a)): a[i] += 3
- Pythonic
a = [3, 4, 5] a = [i + 3 for i in a] # Or: a = map(lambda i: i + 3, a)
文件讀取
- Bad
f = open('file.txt') a = f.read() print a f.close()
- Pythonic
with open('file.txt') as f: for line in f: print line
代碼續行
- Bad
my_very_big_string = """For a long time I used to go to bed early. Sometimes, \ when I had put out my candle, my eyes would close so quickly that I had not even \ time to say “I’m going to sleep.”""" from some.deep.module.inside.a.module import a_nice_function, another_nice_function, \ yet_another_nice_function
- Pythonic
my_very_big_string = ( "For a long time I used to go to bed early. Sometimes, " "when I had put out my candle, my eyes would close so quickly " "that I had not even time to say “I’m going to sleep.”" ) from some.deep.module.inside.a.module import ( a_nice_function, another_nice_function, yet_another_nice_function)
顯式代碼
- Bad
def make_complex(*args): x, y = args return dict(**locals())
- Pythonic
def make_complex(x, y): return {'x': x, 'y': y}
使用佔位符
- Pythonic
filename = 'foobar.txt' basename, _, ext = filename.rpartition('.')
鏈式比較
- Bad
if age > 18 and age < 60: print("young man")
- Pythonic
if 18 < age < 60: print("young man")
- 理解了鏈式比較操作，那麼你應該知道爲什麼下面這行代碼輸出的結果是 False
>>> False == False == True
False
三目運算
這個保留意見。隨使用習慣就好。
- Bad
if a > 2: b = 2 else: b = 1 #b = 2
- Pythonic
a = 3 b = 2 if a > 2 else 1 #b = 2