15個Pythonic的代碼示例(值得收藏)
Python由于語言的簡潔性,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(yōu)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(yōu)秀的源代碼值得閱讀,比如:requests、flask、tornado,這里小明收集了一些常見的 Pythonic 寫法,幫助你養(yǎng)成寫優(yōu)秀代碼的習(xí)慣。
01. 變量交換
Bad
tmp = a a = b b = tmp
Pythonic
a,b = b,a
02. 列表推導(dǎo)
Bad
my_list = [] for i in range(10): my_list.append(i*2)
Pythonic
my_list = [i*2 for i in range(10)]
03. 單行表達(dá)式
雖然列表推導(dǎo)式由于其簡潔性及表達(dá)性,被廣受推崇。
但是有許多可以寫成單行的表達(dá)式,并不是好的做法。
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
04. 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)
05. 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
06. 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)
07. 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!'
08. 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']
09. 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)
10. 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
11. 代碼續(xù)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)
12. 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}
13. 使用占位符
Pythonic
filename = 'foobar.txt' basename, _, ext = filename.rpartition('.')
14. 鏈?zhǔn)奖容^
Bad
if age > 18 and age < 60: print("young man")
Pythonic
if 18 < age < 60: print("young man")
理解了鏈?zhǔn)奖容^操作,那么你應(yīng)該知道為什么下面這行代碼輸出的結(jié)果是 False
>>> False == False == True False
15. 三目運算
這個保留意見。隨使用習(xí)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
參考文檔
http://docs.python-guide.org/en/latest/writing/style/
https://foofish.net/idiomatic_part2.html
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