Unable to use pip to install packages

[Md Sohail Ansari via Python-list]

Hi Team,
Thanks for your support. I am having trouble installing any packages using pip 
in Python 3.x (earlier had Python 3.8.3, so changed to 3.8.8) in Windows 10.
Please help me with below issues:
-----------------------------------------------C:\Users\mohsohai>pip install 
pytestTraceback (most recent call last):  File 
"C:\Users\mohsohai\AppData\Local\Programs\Python\Python38\Scripts\pip-script.py",
 line 11, in <module>    load_entry_point('pip==21.0.1', 'console_scripts', 
'pip')()  File 
"c:\users\mohsohai\appdata\local\programs\python\python38\lib\site-packages\pip\_internal\cli\main.py",
 line 71, in main    command = create_command(cmd_name, isolated=("--isolated" 
in cmd_args))  File 
"c:\users\mohsohai\appdata\local\programs\python\python38\lib\site-packages\pip\_internal\commands\__init__.py",
 line 96, in create_command    module = importlib.import_module(module_path)  
File 
"c:\users\mohsohai\appdata\local\programs\python\python38\lib\importlib\__init__.py",
 line 127, in import_module    return _bootstrap._gcd_import(name[level:], 
package, level)  File "<frozen importlib._bootstrap>", line 1014, in 
_gcd_import  File "<frozen importlib._bootstrap>", line 991, in _find_and_load  
File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked  
File "<frozen importlib._bootstrap>", line 671, in _load_unlocked  File 
"<frozen importlib._bootstrap_external>", line 783, in exec_module  File 
"<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed  File 
"c:\users\mohsohai\appdata\local\programs\python\python38\lib\site-packages\pip\_internal\commands\install.py",
 line 12, in <module>    from pip._internal.cache import 
WheelCacheModuleNotFoundError: No module named 
'pip._internal.cache'-------------------------------------------------
Note: Have included pip in Enviromnet Variables
Thank you,Sohail.
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