First point in the release notes:

&gt; - Switch to a Calendar based versioning scheme.
&gt;
&gt; https://pip.pypa.io/en/stable/news/

More about calendar versioning: https://calver.org/

I know, [androidx and support dependency causing multidex error][1]
We can not use androidx and android support at a same time. So I totally migrate to androidx. but one of my dependency lib used android support &quot;lottie&quot;.

What can we do in above situation? Should I remove &#39;lottie&#39; from my project.

below is my gradle

 

    defaultConfig {
            minSdkVersion 19
            targetSdkVersion 28
            versionCode 1
            versionName &quot;1.0&quot;
            testInstrumentationRunner &quot;android.support.test.runner.AndroidJUnitRunner&quot;
            vectorDrawables.useSupportLibrary = true
            multiDexEnabled true
        }

        ext{
        lottieVersion = &quot;2.5.4&quot;
    }
    

    dependencies {
        implementation fileTree(dir: &#39;libs&#39;, include: [&#39;*.jar&#39;])
        implementation &quot;org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version&quot;
    
        def androidx = &quot;1.0.0-rc01&quot;
        api &quot;androidx.constraintlayout:constraintlayout:1.1.2&quot;
        api &quot;androidx.appcompat:appcompat:$androidx&quot;
        api &quot;androidx.recyclerview:recyclerview:$androidx&quot;
        api &quot;androidx.cardview:cardview:$androidx&quot;
        api &quot;androidx.core:core-ktx:$androidx&quot;
        api &quot;com.google.android.material:material:1.0.0-rc01&quot;
        implementation &quot;com.google.code.gson:gson:2.8.5&quot;
        implementation &quot;androidx.multidex:multidex:2.0.0&quot;
        implementation &quot;com.airbnb.android:lottie:$lottieVersion&quot;
        }

  [1]: https://stackoverflow.com/questions/50387207/error-while-merging-dex-program-type-already-present-android-support-v4-os-resu



Can I use library that used android support with Androidx projects.

Seeking confirmation or clarification

If I have two interfaces. What is the &quot;proper&quot; way to create a merge of those two interfaces? 

&lt;!-- language: lang-ts --&gt;

    IFoo {
      // some stuff
    }


    IBar {
      // some stuff
    }


    IFooBar extends IFoo, IBar {
     // Empty
    }


It works but it feels weird, like I am doing it wrong with the empty IFooBar. 

Am I doing this correctly?

*I also noticed that this also works:*

&lt;!-- language: lang-ts --&gt;

    type IFooBar = IFoo &amp; IBar;

I have an illogical aversion to using `type` yet, it is much cleaner. 


Merge Two Interfaces

while running a `pip install` script I get the following warning: 

     You are using pip version 10.0.1, however version 18.0 is available

This is very strange. Did the pip project just upgrade from version 10 to version 18? Why?

Why did pip upgrade from version 10 to version 18?

while running a <code>pip install</code> script I get the following warning:
<pre><code class="hljs language-arduino"> You are using pip version 10.0.1, however version 18.0 is available
</code></pre>
This is very strange. Did the pip project just upgrade from version 10 to version 18? Why?

(*Probably a noob question, but I didn&#39;t find a solution after googling for 20 minutes.*)

I created a new *pure Python* project with PyCharm which yielded the following folder structure

    myproject
    └── venv
        ├── bin
        │&#160;&#160; ├── activate
        │&#160;&#160; ├── activate.csh
        │&#160;&#160; ├── activate.fish
        │&#160;&#160; ├── easy_install
        │&#160;&#160; ├── easy_install-3.5
        │&#160;&#160; ├── pip
        │&#160;&#160; ├── pip3
        │&#160;&#160; ├── pip3.5
        │&#160;&#160; ├── python
        │&#160;&#160; ├── python3
        │&#160;&#160; └── python3.5
        ├── include
        ├── lib
        │&#160;&#160; └── python3.5
        ├── lib64 -&gt; lib
        └── pyvenv.cfg

Where do I put `myproject.py` or the `myproject` folder now?

- Inside or outside of `venv`?
- In the `venv/bin`folder?
- Just inside `venv`, i.e. `myproject/venv/myproject.py`?

Where do I put my python files in the venv folder?

Inputting the command `0xbin()` returns False:

    &gt;&gt;&gt; 0xbin()
    False

Why does that happen? This syntax should have no meaning whatsoever. Functions cannot start with 0, there are no &quot;i&quot; and &quot;n&quot; in hex, and the bin function must have some arguments.

In python, why does 0xbin() return False?

I created two lists `l1` and `l2`, but each one with a different creation method:

    import sys
    
    l1 = [None] * 10
    l2 = [None for _ in range(10)]
    
    print(&#39;Size of l1 =&#39;, sys.getsizeof(l1))
    print(&#39;Size of l2 =&#39;, sys.getsizeof(l2))

But the output surprised me:

    Size of l1 = 144
    Size of l2 = 192

The list created with a list comprehension is a bigger size in memory, but the two lists are identical in Python otherwise.

Why is that? Is this some CPython internal thing, or some other explanation?

Why do two identical lists have a different memory footprint?

I am using [`pipenv`](https://pipenv.kennethreitz.org/) to handle Python package dependencies.

The Python package is using two packages (named `pckg1` and `pckg2`) that rely on the same package named `pckg3`, **but from two different versions**. Showing the dependency tree :

    $ pipenv graph
      pckg1==3.0.0
        - pckg3 [required: &gt;=4.1.0]
      pckg2==1.0.2
        - pckg3 [required: ==4.0.11]

An attempt to install dependencies :

    $ pipenv install

    Warning: Your dependencies could not be resolved. You likely have a mismatch in your sub-dependencies.
    You can use $ pipenv install --skip-lock to bypass this mechanism, then run $ pipenv graph to inspect the situation.
    Hint: try $ pipenv lock --pre if it is a pre-release dependency.
    Could not find a version that matches pckg3==4.0.11,==4.1.0,&gt;=4.1.0 (from -r C:\Users\user\AppData\Local\Temp\pipenv-o7uxm080-requirements\pipenv-hwekv7dc-constraints.txt (line 2))
    Tried: 3.3.1, 3.3.2, 3.3.3, 3.4.0, 3.4.2, 4.0.0, 4.0.0, 4.0.1, 4.0.1, 4.0.2, 4.0.2, 4.0.3, 4.0.3, 4.0.4, 4.0.4, 4.0.6, 4.0.6, 4.0.8, 4.0.8, 4.0.9, 4.0.9, 4.0.10, 4.0.10, 4.0.11, 4.0.11, 4.1.0, 4.1.0, 4.1.1, 4.1.1, 4.1.2, 4.1.2, 4.2.1, 4.2.1, 4.3.0, 4.3.0
    There are incompatible versions in the resolved dependencies.

As suggested, `pip install --skip-lock` does the trick, but the dependency tree is still unresolved.

I would love to tell `Pipenv` to override `pckg2`&#39;s requirement, and specify `pckg3&gt;=4.1.0`.

How can this be resolved?

How to resolve Python package dependencies with pipenv?

I&#39;m currently trying my hands on the new dataclass constructions introduced in Python 3.7. I am currently stuck on trying to do some inheritance of a parent class. It looks like the order of the arguments are botched by my current approach such that the bool parameter in the child class is passed before the other parameters. This is causing a type error.

    from dataclasses import dataclass
    
    @dataclass
    class Parent:
        name: str
        age: int
        ugly: bool = False
    
        def print_name(self):
            print(self.name)
    
        def print_age(self):
            print(self.age)
    
        def print_id(self):
            print(f&#39;The Name is {self.name} and {self.name} is {self.age} year old&#39;)
    
    @dataclass
    class Child(Parent):
        school: str
        ugly: bool = True
    

    jack = Parent(&#39;jack snr&#39;, 32, ugly=True)
    jack_son = Child(&#39;jack jnr&#39;, 12, school = &#39;havard&#39;, ugly=True)
    
    jack.print_id()
    jack_son.print_id()


When I run this code I get this `TypeError`:

    TypeError: non-default argument &#39;school&#39; follows default argument

How do I fix this?

Class inheritance in Python 3.7 dataclasses

There are two `pip install` options related to reinstalling the packages, which are `--ignore-installed` and `--force-reinstall`.

These two options described as following in the official doc

    --force-reinstall
    Reinstall all packages even if they are already up-to-date.
    
    -I, --ignore-installed
    Ignore the installed packages (reinstalling instead).

It seems that they all ignore something and do the reinstallation but I cannot tell the difference between them (I can see some difference if I actually execute them ... but I cannot explain). If I search &quot;force reinstall packages in pip&quot;, the result lists both `--ignore-installed` and `--force-reinstall`, which confuses me for a long time.

Difference between pip install options &quot;ignore-installed&quot; and &quot;force-reinstall&quot;

The problem originates when I start by cloning a git project that uses pipenv, so it has a Pipfile + Pipfile.lock. I want to use a virtual environment with the project so I run `pipenv shell`. I now have a virtual environment created and I am inside the virtual environment. The project obviously has a lot of dependencies (listed in the Pipfile). I don&#39;t want to have to go through the list in the Pipfile one by one and install them using `pipenv install &lt;package_name&gt;`. Is there a pipenv/pip command that installs all the packages from a Pipfile I already have? Or maybe I need to set up the environment differently than running `pipenv shell`?

How to install dependencies from a copied pipfile inside a virtual environment?

In my MacOS Mojave terminal I wanted to install a python package with pip. At the end it says:

    You are using pip version 10.0.1, however version 18.1 is available.
    You should consider upgrading via the &#39;pip install --upgrade pip&#39; command.

So I wanted to update pip with the given command but I got an error:

    Could not install packages due to an EnvironmentError: [Errno 13] Permission denied: 
    &#39;/Library/Python/2.7/site-packages/pip-18.0-py2.7.egg/EGG-INFO/PKG-INFO&#39;
    Consider using the `--user` option or check the permissions.

I don&#39;t really understand what to do now. **Also I realized it says Python 2.7 in the error message but I have and want to use only python 3.**

Could not install packages due to an EnvironmentError: [Errno 13]

This is a truly popular question here at SO, but none of the many answers I have looked at, clearly explain what this error really mean, and why it occurs. 

One source of confusion, is that when (for example) you do `pip install pycparser`, you first get the error:

**`Failed building wheel for pycparser`**

which is then followed by the message that the package was: 

**`Successfully installed pycparser-2.19`**.

---

&lt;!-- language: none --&gt;

    # pip3 install pycparser
    
    Collecting pycparser
      Using cached https://files.pythonhosted.org/packages/68/9e/49196946aee219aead1290e00d1e7fdeab8567783e83e1b9ab5585e6206a/pycparser-2.19.tar.gz
    Building wheels for collected packages: pycparser
      Running setup.py bdist_wheel for pycparser ... error
      Complete output from command /usr/bin/python3 -u -c &quot;import setuptools, tokenize;__file__=&#39;/tmp/pip-install-g_v28hpp/pycparser/setup.py&#39;;f=getattr(tokenize, &#39;open&#39;, open)(__file__);code=f.read().replace(&#39;\r\n&#39;, &#39;\n&#39;);f.close();exec(compile(code, __file__, &#39;exec&#39;))&quot; bdist_wheel -d /tmp/pip-wheel-__w_f6p0 --python-tag cp36:
      Traceback (most recent call last):
        File &quot;&lt;string&gt;&quot;, line 1, in &lt;module&gt;
        ...
        File &quot;/usr/lib/python3.6/site-packages/pkg_resources/__init__.py&quot;, line 2349, in resolve
          module = __import__(self.module_name, fromlist=[&#39;__name__&#39;], level=0)
      ModuleNotFoundError: No module named &#39;wheel.bdist_wheel&#39;
    
      ----------------------------------------
      Failed building wheel for pycparser
      Running setup.py clean for pycparser
    Failed to build pycparser
    Installing collected packages: pycparser
      Running setup.py install for pycparser ... done
    Successfully installed pycparser-2.19


**What is going on here?**

(I would like to understand how something can fail but still get installed and whether you can trust this package functioning correctly?)

So far the best partial explanation I have found is [this](https://stackoverflow.com/a/37693431/).


Content Type	Original Author	Original Content on Stackoverflow
Question	mircealungu	View Question on Stackoverflow
Solution 1 - Python	deceze	View Answer on Stackoverflow

Why did pip upgrade from version 10 to version 18?

Python Problem Overview

Python Solutions

Solution 1 - Python

Merge Two Interfaces

Can I use library that used android support with Androidx projects.

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