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15个Pythonic的代码示例(值得收藏)

时间:2020-11-20 11:29:30      阅读:6      评论:0      收藏:0      [点我收藏+]

标签:module   lex   value   变量   filter   表达式   mod   pythonic   iso   

01. 变量交换

Bad

tmp = a
a = b
b = tmp

Pythonic

a,b = b,a

02. 列表推导

Bad

my_list = []
for i in range(10):
  my_list.append(i*2)

Pythonic

my_list = [i*2 for i in range(10)]

03. 单行表达式

虽然列表推导式由于其简洁性及表达性,被广受推崇。

但是有许多可以写成单行的表达式,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

04. 带索引遍历

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. 真假判断

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. 访问字典元素

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. 文件读取

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. 代码续行

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. 显式代码

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. 链式比较

Bad

if age > 18 and age < 60:
  print("young man")

Pythonic

if 18 < age < 60:
  print("young man")

理解了链式比较操作,那么你应该知道为什么下面这行代码输出的结果是 False

>>> False == False == True 
False

15. 三目运算

Bad

if a > 2:
  b = 2
else:
  b = 1
#b = 2 

Pythonic

a = 3  
 
b = 2 if a > 2 else 1
#b = 2 

 

15个Pythonic的代码示例(值得收藏)

标签:module   lex   value   变量   filter   表达式   mod   pythonic   iso   

原文地址:https://www.cnblogs.com/tracydzf/p/13976215.html

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