Python - 10 Tips and Tricks (Set 1)

Tip 1:

Get the list of all the installed packages:
(base) C:\Users\ashish>pip freeze
alabaster==0.7.12
...
gevent==1.3.7
...

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Tip 2:

You can list all discoverable environments with:
"conda info --envs"
"conda info -e"
"conda env list"

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Tip 3:

FIND ALL THE AVAILABLE RELEASES OF A PYTHON PACKAGE:

(base) C:\Users\ashish>pip install scikit-learn==
Collecting scikit-learn==
  Could not find a version that satisfies the requirement scikit-learn== (from versions: 0.9, 0.10, 0.11, 0.12, 0.12.1, 0.13, 0.13.1, 0.14, 0.14.1, 0.15.0b1, 0.15.0b2, 0.15.0, 0.15.1, 0.15.2, 0.16b1, 0.16.0, 0.16.1, 0.17b1, 0.17, 0.17.1, 0.18, 0.18.1, 0.18.2, 0.19b2, 0.19.0, 0.19.1, 0.19.2, 0.20rc1, 0.20.0, 0.20.1, 0.20.2, 0.20.3, 0.21rc2, 0.21.0, 0.21.1, 0.21.2)
No matching distribution found for scikit-learn==

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Tip 4:

You can set the "workspace" directory from where the Jupyter Notebook will pick up the notebooks.

In our case, open this file: "C:\Users\Admin\.jupyter\jupyter_notebook_config.py"

Search for property: "c.NotebookApp.notebook_dir".

Set this to the directory where your ".ipynb" files are kept.

Ref: https://stackoverflow.com/questions/15680463/change-ipython-jupyter-notebook-working-directory 

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Tip 5:

To remove all unused imports from your Python script:

(base) C:\Users\ashish\Desktop\Workspace>autoflake --in-place Script.py

$ autoflake --in-place --remove-all-unused-imports Script.py

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Tip 6:

To check the version of Anaconda installation:

(base) C:\Users\ashish>conda --version
conda 4.7.5

(base) C:\Users\ashish>conda info

     active environment : base
    active env location : C:\Users\ashish\AppData\Local\Continuum\anaconda3
            shell level : 1
       user config file : C:\Users\ashish\.condarc
 populated config files :
          conda version : 4.7.5
    conda-build version : 3.17.6
         python version : 3.7.1.final.0
       virtual packages :
       base environment : C:\Users\ashish\AppData\Local\Continuum\anaconda3  (writable)
           channel URLs : https://repo.anaconda.com/pkgs/main/win-64
                          https://repo.anaconda.com/pkgs/main/noarch
                          https://repo.anaconda.com/pkgs/r/win-64
                          https://repo.anaconda.com/pkgs/r/noarch
                          https://repo.anaconda.com/pkgs/msys2/win-64
                          https://repo.anaconda.com/pkgs/msys2/noarch
          package cache : C:\Users\ashish\AppData\Local\Continuum\anaconda3\pkgs
                          C:\Users\ashish\.conda\pkgs
                          C:\Users\ashish\AppData\Local\conda\conda\pkgs
       envs directories : C:\Users\ashish\AppData\Local\Continuum\anaconda3\envs
                          C:\Users\ashish\.conda\envs
                          C:\Users\ashish\AppData\Local\conda\conda\envs
               platform : win-64
             user-agent : conda/4.7.5 requests/2.21.0 CPython/3.7.1 Windows/10 Windows/10.0.16299
          administrator : False
             netrc file : None
           offline mode : False

Ref: https://stackoverflow.com/questions/48342098/how-to-check-python-anaconda-version-installed-on-windows-10-pc?rq=1

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Tip 7:

FOR LOADING A DIRECTORY AS PYTHON PACKAGE, IT SHOULD HAVE A FILE CALLED '__init__.py' THAT CAN BE AN EMPTY FILE.

Usage:
Suppose 'rnn_dir' is a directory with 'brown.py' file having a function 'get_sentences', then we can write the following line of code to import it:
 
from rnn_dir.brown import get_sentences

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Tip 8:

How do you append directories to your Python path?

Answer:

Your path (i.e. the list of directories Python goes through to search for modules and files) is stored in the path attribute of the sys module. Since path is a list, you can use the append method to add new directories to the path.

For instance, to add the directory /home/me/mypy to the path, just do:

import sys
sys.path.append("/home/me/mypy")

Ref: https://www.johnny-lin.com/cdat_tips/tips_pylang/path.html

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Tip 9: 

How do get the absolute path to your present working directory?

Answer:

(base) C:\Users\ashish>python
Python 3.7.1 (default, Dec 10 2018, 22:54:23) [MSC v.1915 64 bit (AMD64)] :: Anaconda, Inc. on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.path.abspath('..')
'C:\\Users'
>>> os.path.abspath('.')
'C:\\Users\\ashish'
>>> os.path.abspath('')
'C:\\Users\\ashish'
>>> os.path.abspath()
Traceback (most recent call last):
  File "[stdin]", line 1, in [module]
TypeError: abspath() missing 1 required positional argument: 'path'
>>>

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Tip 10:

WHEN TO USE NP.ISNAN AND PD.ISNULL?

np.isnan can be applied to NumPy arrays of native dtype (such as np.float64):

In [99]: np.isnan(np.array([np.nan, 0], dtype=np.float64))
Out[99]: array([True, False], dtype=bool)

But it raises TypeError when applied to object arrays:

In [96]: np.isnan(np.array([np.nan, 0], dtype=object))
TypeError: ufunc 'isnan' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''safe''

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