Reading all values from certain columns in csv into one array python

Question

I have data in csv format of the following form:

A   B   a1  a2  a3  a4  a5
1   0   100 34  44  1   1
2   0   101 1   44  11  3
3   0   105 3   55  21  22
4   0   45  4   52  1   45
5   0   57  5   42  3   56
6   0   89  78  1   3   67
7   0   34  99  2   4   98
8   0   57  23  2   5   2

I would like to store the data from columns a1 on in one array to give:

I can do this using python by reading the columns I want from the csv into a pandas dataframe. Converting each column into an array, looping through each array, and appending the values to one new array. I know this is very inefficient. Is there a better way to do this? Thanks!

jezrael · Accepted Answer · 2018-05-11 13:58:45Z

2

Use numpy.ravel with selecting columns by columns names:

A = df[['a2', 'a3', 'a4', 'a5']].values.ravel()

Or by filter:

A = df.filter(like='a').values.ravel()

Or by position - from second column to end:

A = df.iloc[:, 2:].values.ravel()

print (A)
[100  34  44   1   1 101   1  44  11   3 105   3  55  21  22  45   4  52
   1  45  57   5  42   3  56  89  78   1   3  67  34  99   2   4  98  57
  23   2   5   2]

answered May 11, 2018 at 13:58

jezrael

868k103 gold badges1.4k silver badges1.3k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

jezrael Over a year ago

@Sjoseph - Glad can help! Small advice - For prevent downvotes add some code, error, what you try.

Collectives™ on Stack Overflow

Reading all values from certain columns in csv into one array python

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related