6. 字典键值判断

##不推荐

if my_dict.has_key(key):

# ...do something with d[key]

##推荐

if key in my_dict:

# ...do something with d[key]

7. 字典 get 和 setdefault 方法

##不推荐

navs = {}

for (portfolio, equity, position) in data:

if portfolio not in navs:

navs[portfolio] = 0

navs[portfolio] += position * prices[equity]

##推荐

navs = {}

for (portfolio, equity, position) in data:

# 使用 get 方法

navs[portfolio] = navs.get(portfolio, 0) + position * prices[equity]

# 或者使用 setdefault 方法

navs.setdefault(portfolio, 0)

navs[portfolio] += position * prices[equity]

8. 判断真伪

##不推荐

if x == True:

# ....

if len(items) != 0:

# ...

if items != []:

# ...

##推荐

if x:

# ....

if items:

# ...

9. 遍历列表以及索引

##不推荐

items = 'zero one two three'.split()

# method 1

i = 0

for item in items:

print i, item

i += 1

# method 2

for i in range(len(items)):

print i, items[i]

##推荐

items = 'zero one two three'.split()

for i, item in enumerate(items):

print i, item

10. 列表推导

##不推荐

new_list = []

for item in a_list:

if condition(item):

new_list.append(fn(item))

##推荐

new_list = [fn(item) for item in a_list if condition(item)]