Pandas usecols all 除了最后一个
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Pandas usecols all except last
提问by Leb
I have a csv file, is it possible to have usecolstake all columns except the last one when utilizing read_csvwithout listing every column needed.
我有一个 csv 文件，是否可以usecols在read_csv不列出需要的每一列的情况下使用除最后一列之外的所有列。
For example, if I have a 13 column file, I can do usecols=[0,1,...,10,11]. Doing usecols=[:-1]will give me syntax error?
例如，如果我有一个 13 列的文件，我可以做usecols=[0,1,...,10,11]. 这样做usecols=[:-1]会给我语法错误吗？
Is there another alternative? I'm using pandas 0.17
还有其他选择吗？我正在使用pandas 0.17
采纳答案by EdChum
You can just read a single line using nrows=1to get the cols and then re-read in the full csv skipping the last col by slicing the column array from the first read:
您可以只读取一行nrows=1以获取 cols，然后通过从第一次读取中切片列数组，在完整的 csv 中重新读取跳过最后一个 col：
cols = pd.read_csv(file, nrows=1).columns
df = pd.read_csv(file, usecols=cols[:-1])
回答by gibbone
Starting from version 0.20the usecolsmethod in pandas accepts a callable filter, i.e. a lambdaexpression. Hence if you know the name of the column you want to skip you can do as follows:
从版本开始，pandas 中0.20的usecols方法接受一个可调用的过滤器，即一个lambda表达式。因此，如果您知道要跳过的列的名称，则可以执行以下操作：
columns_to_skip = ['foo','bar']
df = pd.read_csv(file, usecols=lambda x: x not in columns_to_skip )
Here's the documentation reference.
这是文档参考。
