Retrieving the First Entry in a Dictionary
Indexing dictionaries by numerical indices, such as colors[0], will result in a KeyError since dictionaries are inherently unordered collections. However, Python 3.7 introduced order-preserving dictionaries, offering the ability to access elements in the order of insertion.
Indexing Dictionaries in Python 3.7+
In order-preserving dictionaries, the first key can be retrieved using:
<code class="python">first_key = list(colors.keys())[0] first_value = list(colors.values())[0]</code>
This involves creating a list of the dictionary's keys or values and fetching the first element.
Alternate Method Using a Helper Function
To avoid creating a list, a helper function can be defined as follows:
<code class="python">def get_first_key(dictionary): for key in dictionary: return key raise IndexError</code>
Using the helper function:
<code class="python">first_key = get_first_key(colors) first_value = colors[first_key]</code>
Indexing n-th Element
To retrieve the n-th key, a similar helper function can be employed:
<code class="python">def get_nth_key(dictionary, n=0): if n < 0: n += len(dictionary) for i, key in enumerate(dictionary.keys()): if i == n: return key raise IndexError("dictionary index out of range")</code>
以上是如何檢索 Python 字典中的第一個條目?的詳細內容。更多資訊請關注PHP中文網其他相關文章!