Use either the `typing.TextIO` or `typing.BinaryIO` types, for files opened in text mode or binary mode respectively.

From [the docs](https://docs.python.org/3/library/typing.html#typing.IO):

&gt; ### *class* `typing.IO`
&gt;
&gt; Wrapper namespace for I/O stream types.
&gt;
&gt; This defines the generic type `IO[AnyStr]` and aliases `TextIO` and `BinaryIO` for respectively `IO[str]` and `IO[bytes]`. These representing the types of I/O streams such as returned by `open()`.

The short answer:

 - You need to be explicit.  That is `from typing import TextIO` not just `from typing import *`.
 - Use `IO` to mean a file without specifying what kind
 - Use `TextIO` or `BinaryIO` if you know the type
 - You cannot currently specify it be opened for write or its encoding. 
 
As an example:

    from typing import BinaryIO
    
    def binf(inf: BinaryIO):
        pass
    
    with open(&#39;x&#39;) as f:
        binf(f)

gives an inspection error (in PyCharm) of `Expected type &#39;BinaryIO&#39;, got &#39;TextIO&#39; instead`




I am looking at the new implementations in [**C# 7.0**][1] and I find it interesting that they have implemented local functions but I cannot imagine a scenario where a local function would be preferred over a lambda expression, and what is the difference between the two.

I do understand that lambdas are `anonymous` functions meanwhile local functions are not, but I can&#39;t figure out a real world scenario, where local function has advantages over lambda expressions 

Any example would be much appreciated. Thanks.




  [1]: https://blogs.msdn.microsoft.com/dotnet/2016/08/24/whats-new-in-csharp-7-0/

Local function vs Lambda C# 7.0

I want to convert the following (working) curl snippet to a RestTemplate call:
    
    curl -i -X POST -d &quot;email=first.last@example.com&quot; https://app.example.com/hr/email

How do I pass the email parameter correctly? The following code results in a 404 Not Found response:

    String url = &quot;https://app.example.com/hr/email&quot;;

    Map&lt;String, String&gt; params = new HashMap&lt;String, String&gt;();
    params.put(&quot;email&quot;, &quot;first.last@example.com&quot;);

    RestTemplate restTemplate = new RestTemplate();
    ResponseEntity&lt;String&gt; response = restTemplate.postForEntity( url, params, String.class );

I&#39;ve tried to formulate the correct call in PostMan, and I can get it working correctly by specifying the email parameter as a &quot;form-data&quot; parameter in the body. What is the correct way to achieve this functionality in a RestTemplate?


How to POST form data with Spring RestTemplate?

Is there any correct type hint to use for a file or file-like object in Python? For example, how would I type-hint the return value of this function?

    def foo() -&gt; ???:
        return open(&#39;bar&#39;)


Type hint for a file or file-like object?

Is there any correct type hint to use for a file or file-like object in Python? For example, how would I type-hint the return value of this function?
<pre><code class="hljs language-ruby">def foo() -> ???:
 return open('bar')
</code></pre>

After updating to new version 2016.2, I am getting

    RuntimeWarning: Parent module &#39;tests&#39; not found while handling absolute import
      import unittest
    RuntimeWarning: Parent module &#39;tests&#39; not found while handling absolute import
      import datetime as dt

&#39;tests&#39; is a package inside my main app package, and I receive these warnings when I try to execute unit tests inside this folder. This issue only came up after updating to 2016.2. Besides the warnings, the remaining code works fine.

Edit: This is a known issue - https://youtrack.jetbrains.com/issue/PY-20171. They are suggesting to replace utrunner.py in PyCharm installation folder.

Pycharm import RuntimeWarning after updating to 2016.2

`np.where` has the semantics of a vectorized if/else (similar to Apache Spark&#39;s `when`/`otherwise` DataFrame method). I know that I can use `np.where` on `pandas.Series`, but `pandas` often defines its own API to use instead of raw `numpy` functions, which is usually more convenient with `pd.Series`/`pd.DataFrame`.

Sure enough, I found `pandas.DataFrame.where`. However, at first glance, it has completely different semantics. I could not find a way to rewrite the most basic example of `np.where` using pandas `where`:

    # df is pd.DataFrame
    # how to write this using df.where?
    df[&#39;C&#39;] = np.where((df[&#39;A&#39;]&lt;0) | (df[&#39;B&#39;]&gt;0), df[&#39;A&#39;]+df[&#39;B&#39;], df[&#39;A&#39;]/df[&#39;B&#39;])

Am I missing something obvious? Or is pandas&#39; `where` intended for a completely different use case, despite same name as `np.where`? 

pandas equivalent of np.where

I want to get the first match of a regex.

In this case, I have a list:

    text = &#39;aa33bbb44&#39;
    re.findall(&#39;\d+&#39;,text)
&gt;[&#39;33&#39;, &#39;44&#39;]

I could extract the first element of the list:

    text = &#39;aa33bbb44&#39;
    re.findall(&#39;\d+&#39;,text)[0]
&gt; &#39;33&#39;

But that only works if there is at least one match, otherwise I&#39;ll get an error:

    text = &#39;aazzzbbb&#39;
    re.findall(&#39;\d+&#39;,text)[0]

&gt; IndexError: list index out of range

In which case I could define a function:

    def return_first_match(text):
        try:
            result = re.findall(&#39;\d+&#39;,text)[0]
        except Exception, IndexError:
            result = &#39;&#39;
        return result

Is there a way of obtaining that result without defining a new function?

Return string with first match for a regex, handling case where there is no match

I use the following code to create a numpy-ndarray. The file has 9 columns. I explicitly type each column:

    dataset = np.genfromtxt(&quot;data.csv&quot;, delimiter=&quot;,&quot;,dtype=(&#39;|S1&#39;, float, float,float,float,float,float,float,int))

 Now I would like to get some descriptive statistics for each column (min, max, stdev, mean, median, etc.). Shouldn&#39;t there be an easy way to do this?

I tried this:

    from scipy import stats
    stats.describe(dataset)

but this returns an error: `TypeError: cannot perform reduce with flexible type`

How can I get descriptive statistics of the created NumPy array?

How can I get descriptive statistics of a NumPy array?

If the input is zero I want to make an array which looks like this:

    [1,0,0,0,0,0,0,0,0,0]

and if the input is 5:

    [0,0,0,0,0,1,0,0,0,0]

For the above I wrote:

    np.put(np.zeros(10),5,1)

but it did not work.

Is there any way in which, this can be implemented in one line?


One Hot Encoding using numpy

If I have a function like this:

    def foo(name, opts={}):
      pass

And I want to add type hints to the parameters, how do I do it? The way I assumed gives me a syntax error:

    def foo(name: str, opts={}: dict) -&gt; str:
      pass

The following doesn&#39;t throw a syntax error but it doesn&#39;t seem like the intuitive way to handle this case:

    def foo(name: str, opts: dict={}) -&gt; str:
      pass

I can&#39;t find anything in the [`typing` documentation](https://docs.python.org/3/library/typing.html) or on a Google search. 

Edit: I didn&#39;t know how default arguments worked in Python, but for the sake of this question, I will keep the examples above. In general it&#39;s much better to do the following:

    def foo(name: str, opts: dict=None) -&gt; str:
      if not opts:
        opts={}
      pass

How do I add default parameters to functions when using type hinting?

**UPDATE**: PHP 7.4 now [does support covariance and contravariance][1] which addresses the major issue raised in this question.  

----------

I have run into something of an issue with using return type hinting in PHP 7.  My understanding is that hinting `: self` means that you intend for an implementing class to return itself.  Therefore I used `: self` in my interfaces to indicate that, but when I tried to actually implement the interface I got compatibility errors.  

The following is a simple demonstration of the issue I&#39;ve run into: 

    interface iFoo
    {
    	public function bar (string $baz) : self;
    }
    
    class Foo implements iFoo
    {
    	
    	public function bar (string $baz) : self
    	{
    		echo $baz . PHP_EOL;
    		return $this;
    	}
    }
    
    (new Foo ()) -&gt; bar (&quot;Fred&quot;) 
    	-&gt; bar (&quot;Wilma&quot;) 
    	-&gt; bar (&quot;Barney&quot;) 
    	-&gt; bar (&quot;Betty&quot;);

The expected output was: 

&gt; Fred
&gt; Wilma
&gt; Barney
&gt; Betty

What I actually get is: 

&gt; PHP Fatal error:  Declaration of Foo::bar(int $baz): Foo must be compatible with iFoo::bar(int $baz): iFoo in test.php on line 7

The thing is Foo is an implementation of iFoo, so as far as I can tell the implementation should be perfectly compatible with the given interface.  I could presumably fix this issue by changing either the interface or the implementing class (or both) to return hint the interface by name instead of using `self`, but my understanding is that semantically `self` means &quot;return the instance of the class you just called the method on&quot;.  Therefore changing it to the interface would mean in theory that I could return any instance of something that implements the interface when my intent is for the invoked instance is what will be returned.  

Is this an oversight in PHP or is this a deliberate design decision?  If it&#39;s the former is there any chance of seeing it fixed in PHP 7.1?  If not then what is the correct way of return hinting that your interface expects you to return the instance you just called the method on for chaining?  


  [1]: https://www.php.net/manual/en/language.oop5.variance.php

PHP 7 interfaces, return type hinting and self

Suppose I have a function:

    def get_some_date(some_argument: int=None) -&gt; %datetime_or_None%:
        if some_argument is not None and some_argument == 1:
            return datetime.utcnow()
        else:
            return None

How do I specify the return type for something that can be `None`?

How to specify &quot;nullable&quot; return type with type hints

What&#39;s the difference of using `List`, `Tuple`, etc. from `typing` module:

    from typing import Tuple

    def f(points: Tuple):
        return map(do_stuff, points)

As opposed to referring to Python&#39;s types directly:

    def f(points: tuple):
        return map(do_stuff, points)

And when should I use one over the other?

Using List/Tuple/etc. from typing vs directly referring type as list/tuple/etc

I&#39;m trying to split my huge class into two; well, basically into the &quot;main&quot; class and a mixin with additional functions, like so:

`main.py` file:

    import mymixin.py

    class Main(object, MyMixin):
        def func1(self, xxx):
            ...


`mymixin.py` file:

    class MyMixin(object):
        def func2(self: Main, xxx):  # &lt;--- note the type hint
            ...

Now, while this works just fine, the type hint in `MyMixin.func2` of course can&#39;t work. I can&#39;t import `main.py`, because I&#39;d get a cyclic import and without the hint, my editor (PyCharm) can&#39;t tell what `self` is.

I&#39;m using Python 3.4, but I&#39;m willing to move to 3.5 if a solution is available there.

Is there any way I can split my class into two files and keep all the &quot;connections&quot; so that my IDE still offers me auto-completion and all the other goodies that come from it knowing the types?

Content Type	Original Author	Original Content on Stackoverflow
Question	Mark Amery	View Question on Stackoverflow
Solution 1 - Python	Wayne Werner	View Answer on Stackoverflow
Solution 2 - Python	Charles Merriam	View Answer on Stackoverflow

Type hint for a file or file-like object?

Python Problem Overview

Python Solutions

Solution 1 - Python

Solution 2 - Python

How to POST form data with Spring RestTemplate?

Local function vs Lambda C# 7.0

Attributions