如何在 Python 字典中打印给定值的键？
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How can you print a key given a value in a dictionary for Python?
提问by Jett
For example lets say we have the following dictionary:
例如，假设我们有以下字典：
dictionary = {'A':4,
'B':6,
'C':-2,
'D':-8}
How can you print a certain key given its value?
给定某个键的值，如何打印它？
print(dictionary.get('A')) #This will print 4
How can you do it backwards? i.e. instead of getting a value by referencing the key, getting a key by referencing the value.
你怎么能反过来呢？即不是通过引用键来获取值，而是通过引用值来获取键。
采纳答案by SlxS
I don't believe there is a way to do it. It's not how a dictionary is intended to be used... Instead, you'll have to do something similar to this.
我不相信有办法做到这一点。这不是字典的用途...相反，您必须执行与此类似的操作。
for key, value in dictionary.items():
if 4 == value:
print key
回答by Inbar Rose
The dictionary is organized by: key -> value
字典按以下方式组织：键 -> 值
If you try to go: value -> key
如果你尝试去： value -> key
Then you have a few problems; duplicates, and also sometimes a dictionary holds large (or unhashable) objects which you would not want to have as a key.
那么你有几个问题；重复，有时字典包含您不希望将其作为键的大（或不可散列）对象。
However, if you still want to do this, you can do so easily by iterating over the dicts keys and values and matching them as follows:
但是，如果您仍然想这样做，您可以通过迭代 dicts 键和值并按如下方式匹配它们来轻松实现：
def method(dict, value):
for k, v in dict.iteritems():
if v == value:
yield k
# this is an iterator, example:
>>> d = {'a':1, 'b':2}
>>> for r in method(d, 2):
print r
b
As noted in a comment, the whole thing can be written as a generator expression:
正如评论中所指出的，整个事情可以写成一个生成器表达式：
def method(dict, value):
return (k for k,v in dict.iteritems() if v == value)
Python versions note: in Python 3+ you can use dict.items()instead of dict.iteritems()
Python 版本注意：在 Python 3+ 中，您可以使用dict.items()代替dict.iteritems()
回答by Will Townley
Hey i was stuck on a thing with this for ages, all you have to do is swap the key with the value e.g.
嘿，我多年来一直被困在这件事上，您所要做的就是将键与值交换，例如
Dictionary = {'Bob':14}
you would change it to
你会把它改成
Dictionary ={1:'Bob'}
or vice versa to set the key as the value and the value as the key so you can get the thing you want
反之亦然，将键设置为值，将值设置为键，这样你就可以得到你想要的东西
回答by Fouad Boukredine
In Python 3:
在 Python 3 中：
# A simple dictionary
x = {'X':"yes", 'Y':"no", 'Z':"ok"}
# To print a specific key (for instance the 2nd key which is at position 1)
print([key for key in x.keys()][1])
Output:
输出：
Y
回答by boop
target_key = 4
for i in dictionary:
if dictionary[i]==target_key:
print(i)
回答by karthik bharadwaj
Within a dictionary if you have to find the KEY for the highest VALUE please do the following :
在字典中，如果您必须找到最高 VALUE 的 KEY，请执行以下操作：
- Step 1: Extract all the VALUES into a list and find the Max of list
- Step 2: Find the KEY for the particular VALUE from Step 1
- 步骤 1：将所有 VALUES 提取到列表中并找到列表的最大值
- 第 2 步：从第 1 步中找到特定 VALUE 的 KEY
The visual analyzer of this code is available in this link : LINK
此代码的可视化分析器可在此链接中找到：LINK
dictionary = {'A':4,
'B':6,
'C':-2,
'D':-8}
lis=dictionary.values()
print(max(lis))
for key,val in dictionary.items() :
if val == max(lis) :
print("The highest KEY in the dictionary is ",key)
