Adding a blog post explaining features introduced in Python 3.7

Author: ultimatecoder

_posts/2018-08-12-walkthrough-with-features-introduced-in-core-python-3-7.md

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+---
+layout: post
+title: "Walkthrough with features introduced in Core Python 3.7"
+date: "2018-08-12 15:51:15 +0530"
+tag:
+  - Python
+  - CorePython
+  - Python3.7
+---
+
+
+In this post, I will try to explain improvements done in Core Python version
+3.7. Below is the summary of features covered in this post.
+
+* Breakpoints
+
+* Subprocess
+
+* Dataclass
+
+* Int with underscores
+
+* Namedtuples
+
+* Hash-based Python object file
+
+### breakpoint()
+
+Breakpoints are extream important tool for debugging. Since I started learning
+Python, I am using the same API for putting breakpoints. With this release,
+breakpoint() is introduced as n new built-in function which can be used for
+putting breakpoints in your code.  Putting breakpoint by calling a breakpoint
+function is handier than importing a ```pdf.set_trace()```.
+
+![Breakpoint function in Python 3.7](/assets/images/walkthrough_python_3_7/breakpoint_example.gif)
+
+Code used in above example
+
+```python
+for i in range(100):
+    if i == 10:
+        breakpoint()
+    else:
+        print(i)
+
+```
+
+### PYTHONBREAKPOINT
+
+There wasn't any handy option to
+disable or enable existing breakpoints with single flag. But with this release
+you can certainly reduce your pain by using ```PYTHONBREAKPOINT``` environment
+variable. You can disable all breakpoints in your code by setting the environment variable
+```PYTHONBREAKPOINT``` to ```0```.
+
+
+![Breakpoint environment variable in Python 3.7](/assets/images/walkthrough_python_3_7/breakpoint_environment_variable_example.gif)
+
+##### Note Use "PYTHONBREAKPOINT=0" in your production environment to avoid unwanted pausing at forgotten breakpoints
+
+
+### Subprocess.run(capture_output=True)
+
+You can pipe the output of Standard Output Stream (stdout) and Standard Error
+Stream (stderr) by enabling ```capture_output``` parameter of
+```subprocess.run()``` function.
+
+![subprocess.run got capture_output parameter](/assets/images/walkthrough_python_3_7/subprocess_run_capture_output.gif)
+
+
+### Dataclasses
+
+The new class level decorator ```@dataclass``` introduced with ```dataclasses```
+module. It will reduce many lines of your code.  Python is well-known for
+developing features which allows to achieving more by writing less. Basic
+understanding of Typehints is expected to understand this feature.
+
+The ```@dataclass``` decorator will put obvious construct code. Additionally, it
+will define a behaviour for dander methods ```__repr__()```, ```__eq__()``` and
+```__hash__()``` for us.
+
+
+![Dataclasses.dataclass](/assets/images/walkthrough_python_3_7/dataclasses_dataclass.gif)
+
+Below is the code before introducing a ```dataclasses.dataclass``` decorator.
+
+```python
+class Point:
+
+    def __init__(self, x, y):
+        self.x = x
+        self.y = y
+```
+
+
+After wrapping with ```@dataclass``` decorator it reduces to below code
+
+```python
+from dataclasses import dataclass
+
+
+@dataclass
+class Point:
+    x: float
+    y: float
+```
+
+### Putting underscores in defining Integers:
+
+It is difficult to read when a variable is having a large decimal value. Many
+times I myself put finger on the screen and count the places to get an idea. In
+this version, you can put ```_``` for separating numbers for constructing more
+readable value.
+
+![Integer with underscore](/assets/images/walkthrough_python_3_7/integer_example.gif)
+
+Below is the code used in the example
+
+```python
+x = 1_00_00_00
+print(x)
+```
+
+### Namedtuples
+
+According to me namedtuples are less known, but very helpful feature in Python.
+With this release, you can define default arguments of variables.
+
+![Namedtuples with default arguments](/assets/images/walkthrough_python_3_7/namedtuple_example.gif)
+
+##### Note: Default arguments will be assigned from left to right. In the above example, default value ``2`` will be assigned to variable ``y``
+
+Below is the code used in the example
+
+```python
+from collections import namedtuple
+
+
+Point = namedtuple("Point", ["x", "y"], defaults=[2,])
+p = Point(1)
+print(p)
+```
+
+### .pyc
+
+***.pyc*** are object files generated every time you change your Python code
+file (.py). At present identifying the change in Python code is done by
+comparing meta fields like last edited date and by few other fields. With this
+release, that functionality is improved by comparing files with a hash-based
+approach. Hashed approach is quick and more consistent than a metadata approach.
+Though this improvement is still considered unstable and CPython will continue
+with the metadata approach.