ph 0.0.12

ph - the tabular data shell tool

ph - the tabular data shell tool

Spoiler: Working with tabular data in the command line is difficult. ph makes it easy:

$ pip install ph
$ cat iris.csv | ph columns 4 150 | ph head 15 | ph tail 5 | ph tabulate --headers
      4    150
--  ---  -----
 0  3.7    5.4
 1  3.4    4.8
 2  3      4.8
 3  3      4.3
 4  4      5.8

$ cat iris.csv | ph describe
              150           4      setosa  versicolor   virginica
count  150.000000  150.000000  150.000000  150.000000  150.000000
mean     5.843333    3.057333    3.758000    1.199333    1.000000
std      0.828066    0.435866    1.765298    0.762238    0.819232
min      4.300000    2.000000    1.000000    0.100000    0.000000
25%      5.100000    2.800000    1.600000    0.300000    0.000000
50%      5.800000    3.000000    4.350000    1.300000    1.000000
75%      6.400000    3.300000    5.100000    1.800000    2.000000
max      7.900000    4.400000    6.900000    2.500000    2.000000

Raison d'être

Using the pipeline in Linux is nothing short of a dream in the life of the computer super user.

However the pipe is clearly most suited for a stream of lines of textual data, and not when the stream is actually tabular data.

Tabular data is much more complex to work with due to its dual indexing and the fact that we often read horizontally and often read vertically.

The defacto format for tabular data is csv (which is not perfect in any sense of the word), and the defacto tool for working with tabular data in Python is Pandas.

This is a shell utility ph that reads tabular data from standard in and allows you to perform a pandas function on the data, before writing it to standard out in csv format.

The goal is to create a tool which makes it nicer to work with tabular data in a pipeline.

Example usage

Suppose you have a csv file a.csv that looks like this:

x,y
3,8
4,9
5,10
6,11
7,12
8,13

Transpose:

$ cat a.csv | ph transpose
0,1,2,3,4,5
3,4,5,6,7,8
8,9,10,11,12,13

median (as well as many others, e.g. abs, corr, count, cov, cummax, cumsum, diff, max, product, quantile, rank, round, sum, std, var etc.):

$ cat a.csv | ph median
0
5.5
10.5

Use ph help to list all commands

Using head and tail works approximately as the normal shell equivalents, however they will preserve the header if there is one, e.g.

$ cat a.csv | ph head 7 | ph tail 3
x,y
6,11
7,12
8,13

If the csv file contains a column, e.g. named x containing timestamps, it can be parsed as such with ph date x:

$ cat a.csv | ph date x
x,y
1970-01-01 00:00:00.000000003,8
1970-01-01 00:00:00.000000004,9
1970-01-01 00:00:00.000000005,10
1970-01-01 00:00:00.000000006,11
1970-01-01 00:00:00.000000007,12
1970-01-01 00:00:00.000000008,13

The normal Pandas describe is of course available:

$ cat a.csv | ph describe
              x          y
count  6.000000   6.000000
mean   5.500000  10.500000
std    1.870829   1.870829
min    3.000000   8.000000
25%    4.250000   9.250000
50%    5.500000  10.500000
75%    6.750000  11.750000
max    8.000000  13.000000

Print the column names:

$ cat a.csv | ph columns
x
y

Selecting only certain columns, e.g. a and b

$ cat a.csv | ph columns x y
x,y
3,8
4,9
5,10
6,11
7,12
8,13

Rename:

$ cat a.csv | ph rename x a | ph rename y b
a,b
3,8
4,9
5,10
6,11
7,12
8,13

You can sum two columns x and y and place the result in column z using eval (from `pandas.DataFrame.eval).

$ cat a.csv | ph eval "z = x + y"
z = x + y
x,y,z
3,8,11
4,9,13
5,10,15
6,11,17
7,12,19
8,13,21

$ cat a.csv | ph eval "z = x**2 + y"
x,y,z
3,8,17
4,9,25
5,10,35
6,11,47
7,12,61
8,13,77

If you only want the sum of two columns, then, you can pipe the last two using

$ cat a.csv | ph eval "z = x + y" | ph columns z
z
11
13
15
17
19
21

You can normalize a column using ph normalize col.

$ cat a.csv | ph eval "z = x * y" | ph normalize z
x,y,z
3,8,0.0
4,9,0.15
5,10,0.325
6,11,0.525
7,12,0.75
8,13,1.0