[Personal memo] julia --Using Python library with julia using PyCall

Use Python library

I'm still touching the Mac Book Pro Retina 13 inch with a doy face in the morning. I wondered if I would do julia today as well. Earlier, I wrote in a Qiita article that Python could also be used.

[Personal memo] Try julia Web Application Framework "Morsel"

I thought I'd give it a try, so I'll give it a try. You can run Python libraries using PyCall.jl.

https://github.com/stevengj/PyCall.jl

Let's try it out.

Install PyCall.jl

Execute the following command from Julia's REPL

Pkg.add("PyCall")

This is OK

Try out the Python library

In the example written in README.md of PyCall.jl I am using the math library.

https://github.com/stevengj/PyCall.jl/blob/ef23e044d4870d3440a76c79d09c85a36c510d06/README.md

using PyCall
@pyimport math
math.sin(math.pi / 4) - sin(pi / 4)  # returns 0.0

Can I use a regular expression library?

Try it for the time being

Try out.

using PyCall

@pyimport re

match_pattern = re.compile("Welcome to (.+\.)")

groups_of_match = pycall(match_pattern["search"], PyObject, "Welcome to underground.")["group"]

result = convert(String, pycall(groups_of_match, PyObject, 0))
match_of_group = convert(String, pycall(groups_of_match, PyObject, 1))

println("All match is [$result]")
println("Match of first regex group is [$match_of_group]")

The execution result is as follows.

This code is equivalent to the following in Python:

import re

match_pattern = re.compile("Welcome to (.+\.)")

groups_of_match = match_pattern.search("Welcome to underground.")

result = groups_of_match.group(0)
match_of_group = groups_of_match.group(1)

print("All match is [{result}]".format(result=result))
print("Match of first regex group is [{match_of_group}]".format(
  match_of_group=match_of_group)
)

Execution result

Functions used, etc.

pycall function

According to Reference

pycall(function::PyObject, returntype::Type, args...)

Since it is written in the format, I did the following for the trial of the regular expression library.

pycall(match_pattern["search"], PyObject, "Welcome to underground.")["group"]

PyObject returns numeric, bool, and functional types. It looks like a convenient object. (The explanation says that PyObject of C API is used)

By calling pycall as above, You can use the group that matches the regular expression and the entire string that matches.

match_pattern["search"]Is Get the attributes of the object as described in Description of PyObject. In this case, you are calling the ** search ** method of the regular expression match object.

convert

Convert description is written in the description of PyObject.

convert(T, o::PyObject)

In short, cast. I wanted to make it a string type of julia, so I cast the result of the regular expression (PyObject) to Julia's String type.

convert(String, pycall(groups_of_match, PyObject, 0))

I could easily cast the PyObject type to a String type.

Touch it lightly

Having PyCall seems to be one of julia's complaints. Since julia's own library number is not so large in the built-in one, I thought it was good to be able to use Python library assets ^-^