当我在 pandas 系列中这样做时，价值在哪里? [英] Where is the value when I do this in pandas Series

问题描述

我有以下代码.

s2 = pd.Series([100,"PYTHON","Soochow","Qiwsir"],
               index=["mark","title","university","name"])

s2.mark = "102"

s2.price = "100"

当我打印s2时，可以看到标记的值已更改并且没有价格；但是我可以通过打印s2.price得到结果.为什么不打印price?

When I print s2 , I can see the value of mark was changed and there is no price; but I can get result by printing s2.price. Why is the price not printed?

推荐答案

您正在将属性与系列索引混淆.

You are confusing attributes with series indices.

语法s2.xyz = 100首先在系列 index 中查找xyz，如果存在，则将其覆盖.

The syntax s2.xyz = 100 first looks for xyz in the series index and overwrites it if it exists.

如果不存在，则会在系列中添加新的属性.

If it does not exist, it adds a new attribute to the series.

如何添加属性

if 'price' not in s2:
    s2.price = 100

您不应添加与索引冲突的属性；鉴于允许的访问语法相似，这很麻烦.

You should not add attributes which conflict with indices; this is asking for trouble given the similar syntax permitted for access.

如何向系列添加元素

为了将带有索引的元素添加到系列中，请使用pd.Series.loc:

In order to add an element to the series with an index, use pd.Series.loc:

s2.loc['price'] = 100

如何分辨差异

运行s2.__dict__.您会发现:

{'_data': SingleBlockManager
 Items: Index(['mark', 'title', 'university', 'name'], dtype='object')
 ObjectBlock: 4 dtype: object,
 '_index': Index(['mark', 'title', 'university', 'name'], dtype='object'),
 '_item_cache': {},
 '_name': None,
 '_subtyp': 'series',
 'is_copy': None,
 'price': '100'}

很明显，price是作为属性添加的，而不是作为 index 添加的.

It is clear that price has been added as an attribute, not as an index.

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