擅长:python、mysql、java
<p>如果要检查给定词典中是否存在<code>key</code>,可以执行此操作<code>key in dict</code></p>
<pre><code>currencyCheck = input("Input the currency you would like to use. Ex: 'USD' or 'EUR'...etc ").upper()
currencySYM = {'USD':'$', 'EUR':'€', 'CAN':'C$','YEN':'¥','GBP':'£'}
if currenyCheck in currencySYM:
currencyCheck = currencySYM[key]
else:
exit()
</code></pre>
<p>或者您可以使用<code>.get()</code></p>
<pre><code>currencyCheck = input("Input the currency you would like to use. Ex: 'USD' or 'EUR'...etc ").upper()
currencySYM = {'USD':'$', 'EUR':'€', 'CAN':'C$','YEN':'¥','GBP':'£'}
currencyCheck=currencySYM.get(currencyCheck,exit())
</code></pre>
<blockquote>
<p><strong><em>Dictionaries</em></strong> are unordered - since the <em>values</em> in the <strong><em>dictionary are indexed by keys</em></strong>, they are not held in any particular order, unlike a list, where each item can be located by its position in the list.</p>
</blockquote>