pandas 选择特定列仅形成 Python 中的数据框
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Select Specific Columns only form a dataframe in Python
提问by BioProgram
Using python and pandas as pd, I am trying to OUTPUT a file that has a subset of columns based on specific headers.
使用 python 和 Pandas 作为 pd，我试图输出一个包含基于特定标题的列子集的文件。
Here is an example of an input file
这是输入文件的示例
gene_input = pd.read_table(args.gene, sep="\t" ,index_col=0)
The structure of gene_input:
基因输入的结构：
Sample1 Sample2 Sample3 Sample4 Sample5 Sample6 Sample7 Sample8 Gene1 2 23 213 213 13 132 213 4312 Gene2 3 12 21312 123 123 23 4321 432 Gene3 5 213 21312 15 516 3421 4312 4132 Gene4 2 123 123 7 610 23 3214 4312 Gene5 1 213 213 1 152 23 1423 3421
Using a different loop, I generated TWO dictionaries. The first one has the keys (Sample 1 and Sample 7) and the second has the keys (Sample 4 and 8).
使用不同的循环，我生成了两个字典。第一个具有键（示例 1 和示例 7），第二个具有键（示例 4 和 8）。
I would like to have the following output (Note that I want the samples from each of the dictionaries to be consecutive; i.e. all Dictionary 1 first, then all Dictionary 2): The output that I am looking for is:
我想要以下输出（请注意，我希望每个词典中的样本都是连续的；即首先是所有词典 1，然后是所有词典 2）：我正在寻找的输出是：
Sample1 Sample7 Sample4 Sample8 Gene1 2 213 213 4312 Gene2 3 4321 123 432 Gene3 5 4312 15 4132 Gene4 2 3214 7 4312 Gene5 1 1423 1 3421
I have tried the following but none worked:
我尝试了以下但没有奏效：
key_num=list(dictionary1.keys())
num = genes_input[gene_input.columns.isin(key_num)]
In order to extract the first set of columns then somehow combine it, but that failed. It kept giving me attributes error, and i did update pandas. I also tried the following:
为了提取第一组列，然后以某种方式组合它，但失败了。它一直给我属性错误，我确实更新了Pandas。我还尝试了以下方法：
reader = csv.reader( open(gene_input, 'rU'), delimiter='\t')
header_row = reader.next() # Gets the header
for key, value in numerator.items():
output.write(key + "\t")
if key in header_row:
for row in reader:
idx=header_row.index(key)
output.write(idx +"\t")
as well as some other commands/loops/lines. Sometimes i only get the first key only to be in the output, other times i get an error; depending on which method i tried (i am not listing them all here for sake of convenience).
以及其他一些命令/循环/行。有时我只得到第一个键才出现在输出中，其他时候我得到一个错误；取决于我尝试过的方法（为方便起见，我没有在此处列出所有方法）。
Anyway, if anyone has any input on how I can generate the output file of interest, I'd be grateful.
无论如何，如果有人对我如何生成感兴趣的输出文件有任何意见，我将不胜感激。
Again, here is what I want as a final output:
同样，这是我想要的最终输出：
Sample1 Sample7 Sample4 Sample8 Gene1 2 213 213 4312 Gene2 3 4321 123 432 Gene3 5 4312 15 4132 Gene4 2 3214 7 4312 Gene5 1 1423 1 3421
回答by Dthal
For a specific set of columns in a specific order, use:df = gene_input[['Sample1', 'Sample2', 'Sample4', 'Sample7']]
对于特定顺序的一组特定列，请使用：df = gene_input[['Sample1', 'Sample2', 'Sample4', 'Sample7']]
If you need to make that list (['Sample1',...]) automatically, and the names are as given, you should be able to build the two lists, combine them and then sort:column_names = sorted(dictionary1.keys() + dictionary2.keys())
如果您需要自动制作该列表 (['Sample1',...])，并且名称已给定，您应该能够构建两个列表，将它们组合起来，然后进行排序：column_names = sorted(dictionary1.keys() + dictionary2.keys())
The names that you have should sort correctly. For output, you should be able to use:df.to_csv(<output file name>, sep='\t')
您拥有的名称应该正确排序。对于输出，您应该能够使用：df.to_csv(<output file name>, sep='\t')
EDIT: added part about output
编辑：添加了关于输出的部分
