python-进阶教程-字典中提取子集

0.摘要

本文主要介绍从字典中提取子集的方法。

1.字典推导式（dictionary comprehension）

# example of extracting a subset from a dictionary
from pprint import pprint

prices = {
   'ACME': 45.23,
   'AAPL': 612.78,
   'IBM': 205.55,
   'HPQ': 37.20,
   'FB': 10.75
}

# Make a dictionary of all prices over 200
p1 = { key:value for key, value in prices.items() if value > 200 }

print("All prices over 200")
pprint(p1)
#result：{'AAPL': 612.78, 'IBM': 205.55}

# Make a dictionary of tech stocks
tech_names = { 'AAPL', 'IBM', 'HPQ', 'MSFT' }
p2 = { key:value for key,value in prices.items() if key in tech_names }

print("All techs")
pprint(p2)
#result：{'AAPL': 612.78, 'HPQ': 37.2, 'IBM': 205.55}

2.利用元组序列构建新的字典

from pprint import pprint

prices = {
   'ACME': 45.23,
   'AAPL': 612.78,
   'IBM': 205.55,
   'HPQ': 37.20,
   'FB': 10.75
}

# Make a dictionary of all prices over 200
p1 = dict((key, value)for key, value in prices.items() if value > 200)

print("All prices over 200")
pprint(p1)
#result：{'AAPL': 612.78, 'IBM': 205.55}