错误示例
if (a <= 0):
   return
elif (a > b):
   return
else:
  b -= a

# 正确示例
if (transfer_amount <= 0):
   raise Exception('...')
elif (transfer_amount > balance):
   raise Exception('...')
else:
  balance -= transfer_amount

#错误示例
from mypkg import Obj
from mypkg import my_func

my_func([1, 2, 3])

# 正确示例
import numpy as np
import mypkg

np.array([6, 7, 8])

#错误示例
result = [(x, y) for x in range(10) for y in range(5) if x * y > 10]

# 正确示例
result = []
for x in range(10):
  for y in range(5):
     if x * y > 10:
       result.append((x, y))

#################实验证明，下面代码只在终端中执行Python命令行时才有效，而在执行脚本时整型的数据都会分配同一个空间
#错误示例
x = 27
y = 27
print(x is y) #True

x = 721
y = 721
print(x is y) #False
#以上的代码的改成==,确保是对比对象的值。
#正确示例
x = 27
y = 27
print(x == y)

x = 721
y = 721
print(x == y)

#错误示例
class MyObject(object):
    def __eq__(self, other):
        if other:
            return self.field == other.field
        return True

x = MyObject()
print(x == None)

# 正确示例
x = MyObject()
print(x is None)
正确示例
def pay(name, salary=None):
 if salary is not None:
   salary = 11
 print(name, "is compensated", salary, "dollars")

#错误示例
adict = {i: i * 2 for i in xrange(10000000)}

for key in adict.keys():
   print("{0} = {1}".format(key, adict[key]))

# 正确示例
for key in adict: