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This workflow allows you to switch between multiple Apple accounts quickly and easily in iTunes, App Store and iBooks. 
Also it can automatically turn on iTunes Match (iCloud Music Library) for you after switching (when available).
Passwords will only be stored in Keychain. 
 
Keywords
switch - Switch between Apple accounts in iTunes, App Store and iBooks fill - Autofill the password of your Apple account to the current input area  
Download
v1.5: http://cl.ly/cFsl
v1.4: http://cl.ly/YC2k
v1.3: http://cl.ly/Xqnl
v1.2: http://cl.ly/U5YK
v1.1: http://cl.ly/U4Aw
v1.0: http://cl.ly/U4KK
 
What’s new
Version 1.5 (2015-08-16) - Compatible with iTunes 12.2. - For users who use multiple input languages, now it can change input language to English before switching and autofilling to prevent entering non-ASCII characters, and switch back to previous input language when done. (Thanks to https://github.com/ybian/smartim) - Support non-email Apple ID. Version 1.4 (2014-10-23) - Update to OS X Yosemite's icons and fix some small bugs on Yosemite. Version 1.3 (2014-10-02) - Fix an issue that account and password would be entered into wrong fields in Mac App Store on OS X 10.10 Yosemite. Version 1.2 (2014-02-24) - New keyword "fill" to type in Apple account passwords for you automatically. Version 1.1 (2014-02-23) - Fix a mistake that passwords are stored in the configuration file.  
Packal address
http://www.packal.org/workflow/apple-account-switcher
 
 

 

 

 
Note: Technically, it should be able to support all system languages. But if it doesn't work with your system language, please contact me.

I've written a fairly detailed tutorial on writing Alfred Workflows in Python as part of the documentation for my new Python Workflow library.
Might be of some interest to budding Python Workflow developers, and possibly an interesting trick or two for older hands.

IMPORTANT NOTE ABOUT HANGING PROCESSES ON SIERRA (2017-04-03)
 
Versions of Alfred-Workflow older than 1.25 cannot launch background processes properly on Sierra. In fact, they regularly hang quite dramatically and consume 100% CPU  
 
Users (in particular) affected by this bug should install and run this workflow, which can find and fix any workflows with broken versions of Alfred-Workflow.
 
 
The workflow library for Python
 
GitHub | Documentation

A feature-rich library for developing Alfred workflows in Python

The library is simple to install, has no external dependencies, is very well-documented and maintained, and boasts an eye-wateringly high feature-to-size ratio at under 400 KB. It is the only Python library that is always up-to-date with Alfred's features.

Main features
Supports all Alfred features from 2.0 to 3.6. Catches, logs and notifies users (and developers) of errors in Workflows. No more confusing, silent failure. Super-simple, yet powerful data caching (e.g. from a web service) and storage, including session-scoped data. Easy-to-use Workflow settings API. Supports Alfred's AppleScript API, including saving settings to info.plist and calling External Triggers. Keychain access for secure storage (and cross-machine syncing) of sensitive data, like passwords and API keys. Tunable and understandable Alfred-like fuzzy search (e.g. got matches Game of Thrones as well as Baby Got Back. Or not: that's up to you.) Extremely lightweight, but full-featured, HTTP library with Requests-like interface, but just 12 KB instead of > 2 MB. Convenient access to standard macOS icons, for high-quality, familiar icons without adding size to the library. Also available via proper English. Pre-configured, built-in logging to enable simpler Workflow debugging. Painlessly run (update) scripts in the background without blocking your workflow, so you can still show "old" results while fetching new ones. API for running AppleScript/JXA scripts. Simple support for 3rd-party libraries your Workflow relies on. "Magic" arguments to make developing/debugging Workflows so much easier, especially when helping less technically-inclined users. With "magic" arguments, you and your Workflow's users can open the Workflow's log file in Console.app, its cache and data directories in Finder, and its root directory in Finder or Terminal from the comfort of Alfred's query box. You can also delete the cache/data/settings if something is corrupted. Your workflow can update itself via GitHub releases. Smart handling of non-ASCII. Query sale will match result salé, but query salé will not match result sale. Functions to support migrating settings/data from older versions of your workflow. Alfred 3-only features
Workflow variables Advanced modifiers Alfred 3-only updates Re-run Script Filters  
And as you can see from the above links, there is extensive documentation, including a two-part tutorial on building a Workflow from scratch.

Examples

Here are a few examples of how you can do some pretty cools stuff in just a few lines of code.
A simple Workflow I made to search Packal in ~90 lines of code. A simple Workflow to search your recent Pinboard posts in ~50 lines of code. A polished, user-friendly, wicked-fast Workflow to search your recent Pinboard posts in ~200 lines of code. Remember, each of these Workflows also has—for free—full error-catching and -logging support, and the ability to open its log file (which contains all errors) via Alfred's query box. No need to ask users to grub around in ~/Library or flounder in Terminal here. This is not the Workflow library 2014 deserves, but it's the one it needs   

Feedback

If you have any bug reports/feature requests, add them either here or on GitHub.

More info

The documentation is the definitive source of information on the Alfred-Workflow library. The User Guide and Tutorial provide fairly extensive information both on how to use Alfred-Workflow and write Workflows in general (if you're new to this lark).
 

This workflow allows you to switch between multiple Apple accounts quickly and easily in iTunes, App Store and iBooks. 
Also it can automatically turn on iTunes Match (iCloud Music Library) for you after switching (when available).
Passwords will only be stored in Keychain. 
 
Keywords
switch - Switch between Apple accounts in iTunes, App Store and iBooks fill - Autofill the password of your Apple account to the current input area  
Download
v1.5: http://cl.ly/cFsl
v1.4: http://cl.ly/YC2k
v1.3: http://cl.ly/Xqnl
v1.2: http://cl.ly/U5YK
v1.1: http://cl.ly/U4Aw
v1.0: http://cl.ly/U4KK
 
What’s new
Version 1.5 (2015-08-16) - Compatible with iTunes 12.2. - For users who use multiple input languages, now it can change input language to English before switching and autofilling to prevent entering non-ASCII characters, and switch back to previous input language when done. (Thanks to https://github.com/ybian/smartim) - Support non-email Apple ID. Version 1.4 (2014-10-23) - Update to OS X Yosemite's icons and fix some small bugs on Yosemite. Version 1.3 (2014-10-02) - Fix an issue that account and password would be entered into wrong fields in Mac App Store on OS X 10.10 Yosemite. Version 1.2 (2014-02-24) - New keyword "fill" to type in Apple account passwords for you automatically. Version 1.1 (2014-02-23) - Fix a mistake that passwords are stored in the configuration file.  
Packal address
http://www.packal.org/workflow/apple-account-switcher
 
 

 

 

 
Note: Technically, it should be able to support all system languages. But if it doesn't work with your system language, please contact me.

Oh, I'm so sorry.
That was a mistake. At first, I stored passwords in the json file in order to test this workflow. But in the end I forgot to remove these code from the script.
I've updated a new version to fix it.
Thank you so much for pointing out.

Thank you.
 
However, you said the "Passwords will only be stored in Keychain” but I found my password in a json file (config.json), in plain text, in the workflow data folder… 

Sorry for that. I've fixed it.