How to connect multiple NOX instances in Android studio

About

NOX is a great android emulator. So I am wondering how to replace the default emulator from Android studio with NOX.

How to create multiple nox instances

After installing the NOX, there should be an icon about Multi-drive.

So, double click it and you can add more than one NOX instances just like below

For demonstration (and that’s all I need), there are 2 NOX instances.

How to connect NOX instances

• For each of your NOX instances, following tutorial here to enable the developer mode.

• Keep instances running and head to the console to get the IP:PORT information of your instances by command nox_adb.exe devices just like below

If you don’t know what adb is, here is a link from google to know more about it.

• Link up android studio and NOX instances

After knowing IP:PORT of your NOX instances, you can setup a link for android studio and NOX.

At first, andriod studio cannot detect them after clicking the start button in the red square:

Back to the console, and type command nox_adb.exe connect IP:PORT

Then, you should be able to see them from android studio

Happy coding :P

​

How to do array initialization on python efficiently

Question

Suppose we would like to create an array with 100 elements.

2 types of elements will be tested

• None
• integers from 0 to 99

Methods

3 ways to initialize an array

• By append

def byAppend():
    a = []
    for i in xrange(100):
        a.append(None)

def byAppendInit():
    a = []
    for i in xrange(100):
        a.append(i)

• By list comprehension

def byListComprehension():
    [None for i in xrange(100)]

def byComprehensionInit():
    [i for i in xrange(100)]

• By multiplication

def byMultiplication():
    [None] * 100

def byMultiplicationInit():
    a = [None] * 100
    for i in xrange(100):
        a[i] = i

Results

import timeit
print 'By append'
print(timeit.timeit('byAppend()', setup="from __main__ import byAppend"))
print 'By append init'
print(timeit.timeit('byAppendInit()', setup="from __main__ import byAppendInit"))
print 'By list comprehension'
print(timeit.timeit('byListComprehension()', setup="from __main__ import byListComprehension"))
print 'By list comprehensionInit'
print(timeit.timeit('byComprehensionInit()', setup="from __main__ import byComprehensionInit"))
print 'By byMultiplication'
print(timeit.timeit('byMultiplication()', setup="from __main__ import byMultiplication"))
print 'By byMultiplication init'
print(timeit.timeit('byMultiplicationInit()', setup="from __main__ import byMultiplicationInit"))

Output from consoles

C:\Python27\python.exe C:/Users/Mond/PycharmProjects/hackercup/round1/test.py
By append
10.2452175728
By append init
9.83314044088

By list comprehension
4.45988583823
By list comprehensionInit
4.37547215318

By byMultiplication
0.840903578289
By byMultiplication init
5.83873665989

Conclusion

• If you need to create a “fixed sized” array only, multiplication is the fastest.
• If you need to initialize array with some constants, list comprehension performs better.
• Never ever using the way for appending.

Gotcha

For 2d array initialization, you must be careful not to do it via multiplication.

Below are codes for initializing a 2D array with 3 rows and try to add a string hello to the first array

a = [[]] * 3
a[0].append('hello')
print a

What a will be output is

[['hello'], ['hello'], ['hello']]

instead of

[['hello'], [], []]

Therefore, we can see initializing 2D array via multiplication is not a good way as they are all the same array even though arrays seems to be multiplied (initialized).

The proper way is using list comprehension

# The underscore `_` means I do not care what value it is
a = [[] for _ in xrange(3)]

a[0].append('hello')
print a

Then, a will be output as

[['hello'], [], []]

​

Clean up cache inactive ports

As there is a shortage on my mac book, I need to free storage from mac ports

sudo port -f clean --all all
sudo port -f uninstall inactive

References
http://superuser.com/questions/165652/how-can-i-clean-up-my-macports-installation

​

How to update npm modules

So, when was the last time you have been updated your npm modules?

After I have been updated for few of machines, I believe it is quite useful and necessary for me to record steps for doing so to save my life. Here we go.

1. Get a list of outdated packages

npm provides a useful command for us to do so. Below is an example for listing global modules which are outdated. Of cause, you can run that in your local project once you got the idea.

$ npm -g outdated
Package                 Current  Wanted  Latest  Location
eslint                   3.12.2  3.13.0  3.13.0  /opt/local/lib > eslint
eslint-config-airbnb     13.0.0  14.0.0  14.0.0  /opt/local/lib > eslint-config-airbnb
eslint-plugin-jsx-a11y    2.2.3   3.0.2   3.0.2  /opt/local/lib > eslint-plugin-jsx-a11y
eslint-plugin-react       6.8.0   6.9.0   6.9.0  /opt/local/lib > eslint-plugin-react
npm                     2.15.11   4.0.5   4.0.5  /opt/local/lib > npm

Here is the documentation about npm outdated. Briefly speaking, you should take care versions in the middle column.

NOTE:

• Current column shows versions you own now.
• Wanted column shows latest versions you can get after considering your package dependencies
• Latest column shows the latest available version from corresponding projects

2. Update the npm modules

As my npm is managed by macport, I will let macport to upgrade my npm.

$ sudo port upgrade outdated

Install rest of the modules by specifying name and version together.

$ sudo npm -g install eslint@3.13.0 eslint-config-airbnb@14.0.0 eslint-plugin-jsx-a11y@3.0.2 eslint-plugin-react@6.9.0

NOTE:

• My global modules requires a root privilege

Sometime, there are warnings about mismatched dependencies.

npm WARN eslint-config-airbnb@14.0.0 requires a peer of eslint@^3.13.0 but none was installed.
npm WARN eslint-config-airbnb@14.0.0 requires a peer of eslint-plugin-import@^2.2.0 but none was installed.
npm WARN eslint-config-airbnb-base@11.0.1 requires a peer of eslint@^3.13.0 but none was installed.
npm WARN eslint-config-airbnb-base@11.0.1 requires a peer of eslint-plugin-import@^2.2.0 but none was installed.
npm WARN eslint-plugin-jsx-a11y@3.0.2 requires a peer of eslint@^2.10.2 || 3.x but none was installed.
npm WARN eslint-plugin-react@6.9.0 requires a peer of eslint@^2.0.0 || ^3.0.0 but none was installed.

Don’t be afraid. Make sure they are really a problem first.

$ npm -g list

If you can read those warnings again, they are really problems. Semver explains syntax in the version, for example ^, x etc. I really suggest you to go through that article before solving the warnings.

Basically, they are talking about version mismatched. Take a serious look and install the required packages and problems will be solved.

3. End

You can double check the modules by calling npm outdated again and see whether there are missing modules.

In my opinion, the troublesome parts are resolving versions between packages. This is a smooth and easy process after resolving them.

4. More about npm’s dependencies

Actually, I have posted a question about missing dependencies in StackOverflow here. There are links for you to further study npm’s dependencies. (Hopefully, :D)

5. Search with semver

The best way to know whether the semver includes certain version is testing.

For example, I would like to know how many versions can be search for eslint with ^3.17.x

mondwan@mondwan-All-Series:~/Documents/git/abc$ npm -g view eslint@^3.17.x | grep ^eslint
eslint@3.17.0  
eslint@3.17.1

Change logs

• 2017-03-14: Add a command for searching package’s version
• 2017-03-11: Add a reference from StackOverflow

​