The f-expression

Why f?

It is just fast for you to type, since usually, it is . right after f. Then you have your left hand and right hand working together sequentially.

The Symbolic object f

You can import it by from datar import f, or from datar.all import *

f is a universal Symbolic object, which does the magic to connect the expressions in verb arguments so that they can be delayed to execute.

There are different uses for the f.

• Use as a proxy to refer to dataframe columns (i.e. f.x, f['x'])

• Use as the column name marker for tribble:

  tribble(
      f.x, f.y
      1,   2
      3,   4
  )
  

Note

If you want a sequence literal, other than using base.seq(), you can also use base.c[].

For example,

from datar.base import c
from datar.tibble import tibble
df = tibble(x=c[1:5])  # 1, 2, 3, 4

If you don't like f ...

Sometimes if you have mixed verbs with piping and you want to distinguish to proxies for different verbs:

# you can just replicate f with a different name
g = f

df = tibble(x=1, y=2)
df >> left_join(df >> group_by(f.x), by=g.y)

Or you can instantiate a new Symbolic object:

from pipda.symbolic import Symbolic

g = Symbolic()
# assert f is g

# f and g make no difference in execution technically

You can also alias f by:

from datar import f as g