在Python中对应于列表的词典键值迭代 [英] Iterating Over Dictionary Key Values Corresponding to List in Python

问题描述

在Python中工作2.7。我有一个字典与团队名称作为关键，每个团队的得分和允许的数量作为价值表：

  NL_East = {'Phillies'：[645,469]，'Braves'：[599,546]，'Mets'：[653,672]} 
  

我希望能够将字典提供给一个函数，并遍历每个团队（键）。

这是我正在使用的代码。现在，我只能按队去团队。如何迭代每个团队，并打印每个团队的预期win_percentage？

  def Pythag（联赛）：
 run_scored = float（league ['Phillies'] [0]）
 runs_allowed = float（league ['Phillies'] [1]）$ ​​b $ b win_percentage = round（（runs_scored ** 2）/（（runs_cored ** 2）+（runs_allowed ** 2））* 1000）
打印win_percentage 
  

感谢任何帮助。

解决方案

您有几个选项来迭代字典。

如果您迭代字典本身（为联盟中的团队），您将迭代字典的键。当循环使用for循环时，无论循环使用dict（联盟）本身，行为将是一样的， league.keys（）或 league.iterkeys（）。 dict.iterkeys（） 通常是优先的，因为它是明确而有效的：

  for league.iterkeys（）：
 run_scored，runs_allowed = map（float，league [team]）
  

您还可以遍历两个键并且通过迭代 league.items（）或 league.iteritems（）：

 用于团队，运行在league.iteritems（）中：
 runs_scored，runs_allowed = map（float，runs）
  

您甚至可以在迭代时执行元组拆包：

<$ p $
$ run_scored = float（runs_scored）
runs_allowed = float（runs_allowed）

Working in Python 2.7. I have a dictionary with team names as the keys and the amount of runs scored and allowed for each team as the value list:

NL_East = {'Phillies': [645, 469], 'Braves': [599, 548], 'Mets': [653, 672]}

I would like to be able to feed the dictionary into a function and iterate over each team (the keys).

Here's the code I'm using. Right now, I can only go team by team. How would I iterate over each team and print the expected win_percentage for each team?

def Pythag(league):
    runs_scored = float(league['Phillies'][0])
    runs_allowed = float(league['Phillies'][1])
    win_percentage = round((runs_scored**2)/((runs_scored**2)+(runs_allowed**2))*1000)
    print win_percentage

Thanks for any help.

解决方案

You have several options for iterating over a dictionary.

If you iterate over the dictionary itself (for team in league), you will be iterating over the keys of the dictionary. When looping with a for loop, the behavior will be the same whether you loop over the dict (league) itself, league.keys(), or league.iterkeys(). dict.iterkeys() is generally preferable because it is explicit and efficient:

for team in league.iterkeys():
    runs_scored, runs_allowed = map(float, league[team])

You can also iterate over both the keys and the values at once by iterating over league.items() or league.iteritems():

for team, runs in league.iteritems():
    runs_scored, runs_allowed = map(float, runs)

You can even perform your tuple unpacking while iterating:

for team, (runs_scored, runs_allowed) in league.iteritems():
    runs_scored = float(runs_scored)
    runs_allowed = float(runs_allowed)

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