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In Python, to iterate the dictionary ( dict ) with a for loop, use keys() , values() , items() methods. You can also get a list of all keys and values in the dictionary with those methods and list() . Use the following dictionary as an example. You can iterate keys by using the dictionary object directly in a for loop.
There are two ways of iterating through a Python dictionary object. One is to fetch associated value for each key in keys() list. There is also items() method of dictionary object which returns list of tuples, each tuple having key and value.
To iterate through a dictionary in Python, there are four main approaches you can use: create a for loop, use items() to iterate through a dictionary's key-value pairs, use keys() to iterate through a dictionary's keys, or use values() to iterate through a dictionary's values.
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, or league.keys():
for team in league.keys():
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():
for team, runs in league.items():
runs_scored, runs_allowed = map(float, runs)
You can even perform your tuple unpacking while iterating:
for team, (runs_scored, runs_allowed) in league.items():
runs_scored = float(runs_scored)
runs_allowed = float(runs_allowed)
You can very easily iterate over dictionaries, too:
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)
Dictionaries have a built in function called iterkeys().
Try:
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
Dictionary objects allow you to iterate over their items. Also, with pattern matching and the division from __future__ you can do simplify things a bit.
Finally, you can separate your logic from your printing to make things a bit easier to refactor/debug later.
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
List comprehension can shorten things...
win_percentages = [m**2.0 / (m**2.0 + n**2.0) * 100 for m, n in [a[i] for i in NL_East]]
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