迭代Python中List对应的字典键值

Question

使用 Python 2.7 工作。我有一个字典，其中团队名称作为键，每个团队得分和允许的跑动量作为值列表：

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

我希望能够将字典输入到函数中并迭代每个团队（键）。

这是我正在使用的代码。现在我只能一个队一个队的去。我将如何迭代每个团队并打印每个团队的预期 win_percentage ？

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

感谢您的任何帮助。

Answer 1

您有多种迭代字典的选项。

如果您迭代字典本身（for team in league），您将迭代字典的键。使用 for 循环进行循环时，无论是循环字典 (league) 本身还是 league.keys()：

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

您还可以通过迭代来一次迭代键和值league.items()：

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

您甚至可以在迭代时执行元组解包：

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

Answer 2

您也可以非常轻松地迭代字典：

for team, scores in NL_East.iteritems():
    runs_scored = float(scores[0])
    runs_allowed = float(scores[1])
    win_percentage = round((runs_scored**2)/((runs_scored**2)+(runs_allowed**2))*1000)
    print '%s: %.1f%%' % (team, win_percentage)

Answer 3

字典有一个名为 iterkeys() 的内置函数。

尝试：

for team in league.iterkeys():
    runs_scored = float(league[team][0])
    runs_allowed = float(league[team][1])
    win_percentage = round((runs_scored**2)/((runs_scored**2)+(runs_allowed**2))*1000)
    print win_percentage

Answer 4

字典对象允许您迭代它们的项目。另外，通过模式匹配和 __future__ 的划分，您可以稍微简化一些事情。

最后，您可以将逻辑与打印分开，以便以后更容易重构/调试。

from __future__ import division

def Pythag(league):
    def win_percentages():
        for team, (runs_scored, runs_allowed) in league.iteritems():
            win_percentage = round((runs_scored**2) / ((runs_scored**2)+(runs_allowed**2))*1000)
            yield win_percentage

    for win_percentage in win_percentages():
        print win_percentage

Answer 5

列表理解可以缩短事情......

win_percentages = [m**2.0 / (m**2.0 + n**2.0) * 100 for m, n in [a[i] for i in NL_East]]