如何从没有库仑标题的文本文件中将一个特定的列提取到熊猫数据帧

Question

I created the single csv file -"dataaa.csv", entered column heading "operation" to specify the column i want to extract, and used following code .

data = pd.read_csv('dataaa.csv')
df1=data.loc[:,"operation"]

.its working. but now i want to expand it to a real situation where,

I need to iterate the same procedure over 5210 file which is a result of split command in linux.The output file start with file name xxa. But it dosent contain a column header "operation".How a can i read the column-which is the second column in my file, which is feasible enough to iterate over huge number of files.

Answer 1

You can use the usecols keyword from the read_csv function. See the full documentation .

data = pd.read_csv('dataaa.csv', usecols=[1], header=None)

usecols : array-like or callable, default None

Return a subset of the columns. If array-like, all elements must either be positional (ie integer indices into the document columns) or strings that correspond to column names provided either by the user in names or inferred from the document header row(s). For example, a valid array-like usecols parameter would be [0, 1, 2] or ['foo', 'bar', 'baz'].

If callable, the callable function will be evaluated against the column names, returning names where the callable function evaluates to True. An example of a valid callable argument would be lambda x: x.upper() in ['AAA', 'BBB', 'DDD']. Using this parameter results in much faster parsing time and lower memory usage.