python-编码惯例

python-编码惯例

（1）只有模块作为脚本运行时才执行其中的代码

if __name__ == '__main__':
    print('main')
    #do something

（2）判断逻辑真和逻辑假

if x:
    #do something

if not x:
    #do something

好的代码

name = 'Safe'
pets = ['Dog', 'Cat', 'Hamster']
owners = {'Safe': 'Cat', 'Tom': 'Dog'}
if name and pets and owners:
    print('We have pets.')

不好的代码

name = 'Safe'
pets = ['Dog', 'Cat', 'Hamster']
owners = {'Safe': 'Cat', 'Tom': 'Dog'}
if name != '' and len(pets) > 0 and owners != {}:
    print('We have pets.')

（3）善于使用in操作符

if x in items:
    #do something

for x in items:
    #do something

好的代码

name = 'Safe Hammad'
if 'H' in name:
    print('This name has H in it.')

pets = ['Dog', 'Cat', 'Hamster']
for pet in pets:
    print('A', pet, 'can be very cute!')

不好的代码

name = 'Safe Hammad'
if name.find('H') != -1:
    print('This name has H in it.')

pets = ['Dog', 'Cat', 'Hamster']
i = 0
while i < len(pets):
    print('A', pets[i], 'can be very cute!')
    i += 1

（4）不使用临时变量交互两个变量的值

好的代码

a, b = 1, 2
print(a, b) #1 2
a, b = b, a
print(a, b) #2 1

不好的代码 

a, b = 1, 2
print(a, b) #1 2
temp = a
a = b
b = temp
print(a, b) #2 1

（5）用序列构建字符串

 好的代码

eles = ['a', 'b', 'c', 'd', 'e']
name = ''.join(eles)
print(name) #abcde

不好的代码

eles = ['a', 'b', 'c', 'd', 'e']
name = ''
for ele in eles:
    name += ele
print(name) #abcde

（6）EAFP优于LBYL

EAFP - Easier to Ask Forgiveness than Permission.

LBYL - Look Before You Leap.

好的代码

d = {'x': '5'}
try:
    value = int(d['x'])
except (KeyError, TypeError, ValueError):
    value = None

不好的代码

d = {'x': '5'}
if 'x' in d and 
    isinstance(d['x'], str) and 
    d['x'].isdigit():
    value = int(d['x'])
else:
    value = None

（7）使用enumerate进行迭代

 好的代码

names = ['tom', 'lily', 'marton']
for i, name in enumerate(names):
    print(i, name)

#0 tom
#1 lily
#2 marton

不好的代码

names = ['tom', 'lily', 'marton']
i = 0
for name in names:
    print(i, name)
    i += 1

#0 tom
#1 lily
#2 marton

（8）用解析式生成列表

 好的代码

data = [1, 5, 9, 10, 20, 8]
res = [i for i in data if i % 2 == 0]
print(res) #[10, 20, 8]

不好的代码

data = [1, 5, 9, 10, 20, 8]
res = []
for i in data:
    if i % 2 == 0:
        res.append(i)

print(res) #[10, 20, 8]

（9）用zip组合键和值来创建字典

 好的代码

nums = ['101', '102']
names = ['tom', 'lily'] 
d = dict(zip(nums, names))
print(d) #{'101': 'tom', '102': 'lily'}

 不好的代码

nums = ['101', '102']
names = ['tom', 'lily'] 
d = {}
for i, k in enumerate(nums):
    d[k] = names[i]

print(d) #{'101': 'tom', '102': 'lily'}

参考资料：python惯例

参考资料：python idioms