perfectlysoft/perfect-python

This project provides an expressway to import Python 2.7 module as a Server Side Swift Library.

Acknowledgement

A few updates were suggested by Chris Lattner. Thanks, @Chris.

Linux Build Note

Please make sure libpython2.7-dev was installed on Ubuntu 16.04:

$ sudo apt-get install libpython2.7-dev

MacOS Build Note

Please make sure Xcode 9.0 or later version was installed.

Quick Start

Add PerfectPython dependency to your Package.swift

.package(url: "https://github.com/PerfectlySoft/Perfect-Python.git", 
	from: "3.2.0")

// on target section:
.target(
	// name: "your project name",
	dependencies: ["PerfectPython"]),

Then import two different libraries into the swift source code:

import PythonAPI
import PerfectPython

Before any python api calls, make sure to initialize the library by calling Py_Initialize() function:

Py_Initialize()

Import Python Modules

Use PyObj class to import python modules. In the following example, a python script /tmp/clstest.py has been imported into the current Swift context:

let pymod = try PyObj(path: "/tmp", import: "clstest")

Access Python Variables

Once imported modules, you can use PyObj.load() function to access a variable value, or using PyObj.save() to store a new value to the current python variable.

For example, if there is a variable called stringVar in a python script:

stringVar = 'Hello, world'

Then you can read its value in such a form:

if let str = pymod.load("stringVar")?.value as? String {
	print(str)
	// will print it out as "Hello, world!"
}

You can also directly overwrite the value of the same variable:

try pymod.save("stringVar", newValue: "Hola, 🇨🇳🇨🇦！")

NOTE Currently, Perfect-Python supports the following data types between Swift and Python:

Python Type|Swift Type|Remark ----------|---------|------- int|Int| float|Double| str|String| list|[Any]|Recursively dict|[String:Any]|Recursively

For example, you can convert a Swift String to PyObj by: let pystr = "Hello".python() or let pystr = try PyObj(value:"Hello").

To convert a PyObj to a Swift data type, e.g., a String, there are also two available approaches: let str = pystr.value as? String and let str = String(python: pystr).

Call A Python Function

Method PyObj.call() is available to execute function call with arguments. Consider the python code below:

def mymul(num1, num2):
	return num1 * num2

Perfect-Python can wrap this call by its name as a string and the arguments as an array:

if let res = pymod.call("mymul", args: [2,3])?.value as? Int {
	print(res)
	// the result will be 6
}

Python Object Classes

The same PyObj.load() function helps to access the python class type, however, a following method PyObj.construct() should be called for object instance initialization. This method also supports parameters as an array for python object class construction.

Assume that there is a typical python class called Person, which has two properties name and age, and an object method called intro():

class Person:
	def __init__(self, name, age):
		self.name = name
		self.age = age
		
	def intro(self):
		return 'Name: ' + self.name + ', Age: ' + str(self.age)

To initialize such a class object in Swift, the first two steps look like:

if let personClass = pymod.load("Person"),
    let person = personClass.construct(["rocky", 24]) {
    // person is now the object instance
  }

Then you can access the properties and class methods as common variables and functions do:

if let name = person.load("name")?.value as? String,
    let age = person.load("age")?.value as? Int,
    let intro = person.call("intro", args: [])?.value as? String {
      print(name, age, intro)
}

Callbacks

Consider the following python code as you can execute a function as a parameter like x = caller('Hello', callback):

def callback(msg):
    return 'callback: ' + msg

def caller(info, func):
    return func(info)

The equivalent Swift code is nothing special but using the objective callback function as an argument before calling:

if let fun = pymod.load("callback"),
   let result = pymod.call("caller", args: ["Hello", fun]),
   let v = result.value as? String {
   		print(v)
   	// it will be "callback: Hello"
}

Further Information

For more information on the Perfect project, please visit perfect.org.

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Package Metadata

Repository: perfectlysoft/perfect-python

Default branch: master

README: README.md