entityMap|blocks|key|ckrtq|text|if语句中的name变量被设置为循环后friends的最后一个值，并且if语句只执行一次。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|kaa1|我认为您应该缩进if语句(并打印)，以便在循环的每次迭代中执行该语句|cctsj^0|6|4|J|7|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|J|9|@$A|K|B|L|C|D]|$A|M|B|N|C|D]]|E|@]|F|$]]|$2|G|4|H|6|7|8|O|9|@]|E|@]|F|$]]|$2|I|4|-4|6|7|8|P|9|@]|E|@]|F|$]]]]

The <code>name</code> variable in your if statement is set to the last value of <code>friends</code> after the loop, and the if statement is only executed once.

I think you want to indent the if statement (and print) so that it's executed in each iteration of the loop

entityMap|blocks|key|5hnhg|text|将您的if块再缩进一级。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|9hhiq|...
for+name+in+favourite_languages.keys():
++++print(name.title())
++++if+name+in+friends:
++++++++print("+Hi+"+%2B+name.title()+%2B+",+I+see+your+favourite+language+is+"+%2B
++++++++++++++favourite_languages[name].title()+%2B+"!")|code-block|syntax|javascript|9n1h2^0|3|2|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|M|9|@$A|N|B|O|C|D]]|E|@]|F|$]]|$2|G|4|H|6|I|8|P|9|@]|E|@]|F|$J|K]]|$2|L|4|-4|6|7|8|Q|9|@]|E|@]|F|$]]]]

Indent your <code>if</code> block one level more.

<pre><code>...
for name in favourite_languages.keys():
 print(name.title())
 if name in friends:
 print(" Hi " + name.title() + ", I see your favourite language is " +
 favourite_languages[name].title() + "!")
</code></pre>

entityMap|blocks|key|8r3eg|text|您需要将if语句移到循环中。在其当前状态下，它在外部，因此只能访问name接受的最后一个值。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|c3lq9|此外，我建议您将friends存储为一个集合，以便快速高效地查找。|cslis|In+[193]:+favourite_languages+=+{
+++++...:+++++'jen':'python',
+++++...:+++++'sarah':'c',
+++++...:+++++'edward':'ruby',
+++++...:+++++'phil':'python'
+++++...:+++++}
+++++...:+
+++++...:+friends+=+{'sarah',+'phil'}
+++++...:+for+name+in+favourite_languages.keys():
+++++...:+++++print(name.title())
+++++...:+
+++++...:+++++if+name+in+friends:
+++++...:+++++++++print("+Hi+"+%2B+name.title()+%2B+",+I+see+your+favourite+language+is+"+%2B
+++++...:+++++++++++++++favourite_languages[name].title()+%2B+"!")+
+++++...:+++++++++++
Phil
+Hi+Phil,+I+see+your+favourite+language+is+Python!
Jen
Edward
Sarah
+Hi+Sarah,+I+see+your+favourite+language+is+C!|code-block|syntax|javascript|97ir8|集合具有恒定时间的(O(1))查找，而列表是线性(O(n))。对于您的特定用例，这可能无关紧要，但sets确实能处理大量数据。|908ae|作为进一步的改进，您不需要调用dict.keys()，因为这会为循环创建一个要迭代的键列表，这有点浪费。同样的事情也可以通过以下方式实现：|4qnlt|for+name+in+favourite_languages:|ee8ek|这更简单，效率更高。|burvo^0|4|2|X|4|0|8|7|0|0|9|6|O|6|0|F|B|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|W|9|@$A|X|B|Y|C|D]|$A|Z|B|10|C|D]]|E|@]|F|$]]|$2|G|4|H|6|7|8|11|9|@$A|12|B|13|C|D]]|E|@]|F|$]]|$2|I|4|J|6|K|8|14|9|@]|E|@]|F|$L|M]]|$2|N|4|O|6|7|8|15|9|@$A|16|B|17|C|D]|$A|18|B|19|C|D]]|E|@]|F|$]]|$2|P|4|Q|6|7|8|1A|9|@$A|1B|B|1C|C|D]]|E|@]|F|$]]|$2|R|4|S|6|K|8|1D|9|@]|E|@]|F|$L|M]]|$2|T|4|U|6|7|8|1E|9|@]|E|@]|F|$]]|$2|V|4|-4|6|7|8|1F|9|@]|E|@]|F|$]]]]

You'll need to move your <code>if</code> statement into the loop. In its current state, it is outside, and so will have access to only the last value that <code>name</code> took on. 

Additionally, I recommend you store your <code>friends</code> as a set, for quick and efficient lookup.

<pre><code>In [193]: favourite_languages = {
 ...: 'jen':'python',
 ...: 'sarah':'c',
 ...: 'edward':'ruby',
 ...: 'phil':'python'
 ...: }
 ...: 
 ...: friends = {'sarah', 'phil'}
 ...: for name in favourite_languages.keys():
 ...: print(name.title())
 ...: 
 ...: if name in friends:
 ...: print(" Hi " + name.title() + ", I see your favourite language is " +
 ...: favourite_languages[name].title() + "!") 
 ...: 
Phil
 Hi Phil, I see your favourite language is Python!
Jen
Edward
Sarah
 Hi Sarah, I see your favourite language is C!
</code></pre>

Sets have constant time <code>(O(1))</code> lookup, while lists are linear <code>(O(n))</code>. It may not matter much for your particular use case, but sets really shine with large amounts of data.

As a further improvement, you don't need to call <code>dict.keys()</code>, since that creates a list of keys for the loop to iterate over, which is a little wasteful. The same thing may be achieved with:

<pre><code>for name in favourite_languages:
</code></pre>

This is simpler and more efficient.

entityMap|blocks|key|jffd|text|您需要缩进if+name+in+friends:|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|dtk91|favourite_languages+=+{
++++'jen':'python',
++++'sarah':'c',
++++'edward':'ruby',
++++'phil':'python'
++++}

friends+=+['sarah',+'phil']
for+name+in+favourite_languages.keys():
++++print(name.title())

++++if+name+in+friends:
++++++++print("+Hi+"+%2B+name.title()+%2B+",+I+see+your+favourite+language+is+"+%2B
++++++++++favourite_languages[name].title()+%2B+"!")|code-block|syntax|javascript|3lnh4^0|5|J|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|M|9|@$A|N|B|O|C|D]]|E|@]|F|$]]|$2|G|4|H|6|I|8|P|9|@]|E|@]|F|$J|K]]|$2|L|4|-4|6|7|8|Q|9|@]|E|@]|F|$]]]]

You need to indent <code>if name in friends:</code>

<pre><code>favourite_languages = {
 'jen':'python',
 'sarah':'c',
 'edward':'ruby',
 'phil':'python'
 }

friends = ['sarah', 'phil']
for name in favourite_languages.keys():
 print(name.title())

 if name in friends:
 print(" Hi " + name.title() + ", I see your favourite language is " +
 favourite_languages[name].title() + "!")
</code></pre>

entityMap|blocks|key|96qf9|text|您没有遍历name变量。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|eekck|当您的代码到达if+name+in+friends时，存储在name中的值为phil。|ffa0o|您可以再次循环遍历这些名称(这会产生稍微不同的结果)，或者在代码中添加缩进。|eaa7q|favourite_languages+=+{
'jen':'python',
'sarah':'c',
'edward':'ruby',
'phil':'python'
}

friends+=+['sarah',+'phil']
for+name+in+favourite_languages.keys():
++++print(name.title())

++++if+name+in+friends:
++++++++print("+Hi+"+%2B+name.title()+%2B+",+I+see+your+favourite+language+is+"+%2B
++++++++++++++favourite_languages[name].title()+%2B+"!")|code-block|syntax|javascript|56kub^0|5|4|0|7|I|U|4|12|4|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|Q|9|@$A|R|B|S|C|D]]|E|@]|F|$]]|$2|G|4|H|6|7|8|T|9|@$A|U|B|V|C|D]|$A|W|B|X|C|D]|$A|Y|B|Z|C|D]]|E|@]|F|$]]|$2|I|4|J|6|7|8|10|9|@]|E|@]|F|$]]|$2|K|4|L|6|M|8|11|9|@]|E|@]|F|$N|O]]|$2|P|4|-4|6|7|8|12|9|@]|E|@]|F|$]]]]

You're not looping over the <code>name</code> variable. 

When your code reaches the <code>if name in friends</code>, the value stored in <code>name</code> is <code>phil</code>. 

You could loop over the names again (which would produce a slightly different result), or add a indent to your code. 

<pre><code>favourite_languages = {
'jen':'python',
'sarah':'c',
'edward':'ruby',
'phil':'python'
}

friends = ['sarah', 'phil']
for name in favourite_languages.keys():
 print(name.title())

 if name in friends:
 print(" Hi " + name.title() + ", I see your favourite language is " +
 favourite_languages[name].title() + "!")
</code></pre>

entityMap|blocks|key|69ip5|text|只需将if语句移到for循环中即可。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|7t9cc^0|3|2|9|3|0^^$0|$]|1|@$2|3|4|5|6|7|8|H|9|@$A|I|B|J|C|D]|$A|K|B|L|C|D]]|E|@]|F|$]]|$2|G|4|-4|6|7|8|M|9|@]|E|@]|F|$]]]]

Just move your <code>if</code> statement into your <code>for</code> loop.

entityMap|blocks|key|6oe5a|text|解决方案是，你只需将if条件移到循环中即可。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|cef7r|favourite_languages+=+{
++++'jen':'python',
++++'sarah':'c',
++++'edward':'ruby',
++++'phil':'python'
++++}

friends+=+['sarah',+'phil']
for+name+in+favourite_languages.keys():
++++print(name.title())

++++if+name+in+friends:
++++++++print("+Hi+"+%2B+name.title()+%2B+",+I+see+your+favourite+language+is+"+%2B
++++++++++++++favourite_languages[name].title()+%2B+"!")|code-block|syntax|javascript|fcufr|输出：|fen08|Sarah
+Hi+Sarah,+I+see+your+favourite+language+is+C!
Edward
Jen
Phil
+Hi+Phil,+I+see+your+favourite+language+is+Python!|1h22l^0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|M|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|N|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|O|9|@]|A|@]|B|$]]|$2|J|4|K|6|E|8|P|9|@]|A|@]|B|$F|G]]|$2|L|4|-4|6|7|8|Q|9|@]|A|@]|B|$]]]]

The solution is that you just have to move you if condition inside loop.

<pre><code>favourite_languages = {
 'jen':'python',
 'sarah':'c',
 'edward':'ruby',
 'phil':'python'
 }

friends = ['sarah', 'phil']
for name in favourite_languages.keys():
 print(name.title())

 if name in friends:
 print(" Hi " + name.title() + ", I see your favourite language is " +
 favourite_languages[name].title() + "!")
</code></pre>

Output:

<pre><code>Sarah
 Hi Sarah, I see your favourite language is C!
Edward
Jen
Phil
 Hi Phil, I see your favourite language is Python!
</code></pre>

I produced the following code to loop keys through a dictionary

<pre><code>favourite_languages = {
 'jen':'python',
 'sarah':'c',
 'edward':'ruby',
 'phil':'python'
 }

friends = ['sarah', 'phil']
for name in favourite_languages.keys():
 print(name.title())

if name in friends:
 print(" Hi " + name.title() + ", I see your favourite language is " +
 favourite_languages[name].title() + "!")
</code></pre>

The output produced is 

<pre><code>Jen
Sarah
Edward
Phil
 Hi Phil, I see your favourite language is Python!
</code></pre>

I however, was expecting the following:

<pre><code>Jen
Sarah
 Hi Sarah, I see your favourite language is C!
Edward
Phil
 Hi Phil, I see your favourite language is Python!
</code></pre>

Why does Sarah not come up in the output?

Python Dictionary Loop doesn't work

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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 我生成了以下代码来遍历字典中的键 favourite_languages = {    'jen':'python',    'sarah':'c',    'edward':'ruby',    'phil':'python'    }friends = ['sarah', 'phil']for name in f...

问Python字典循环不起作用
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