Btukfyl

In RStudio, usinglibrary('PythonInR'), and then usingPythonInR::pyConnect()
it shows that the location of the python called is /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7,
however there is no such package in my mac because I've deleted it.

I just want to know how to change the default python path of RStudio when I use PythonInR?

PythonInR has parameters that let you specify your python environment that you want to use with R/R Studio in a variety of ways -

library('PythonInR')

pyConnect(pythonExePath = "C:/ProgramData/Anaconda3/python.exe", dllDir = "C:/ProgramData/Anaconda3", pythonHome = "C:/ProgramData/Anaconda3")`

From the documentation

Arguments

pythonExePath a character containing the path to
"python.exe" (e.g. "C:Python27python.exe")

dllDir an optional
character giving the path to the dll file. Since the dll file is
normally in a system folder or in the same location as python.exe,
this parameter is almost never needed!

pythonHome an optional
character giving the path to PYTHONHOME. On Windows by default
PYTHONHOME is the folder where python.exe is located, therefore this
parameter is normally not needed.

dllName a character giving the name
of the dll file (e.g.d "python27.dll"). majorVersion an integer giving
the major Python version (e.g. 2 or 3).

pyArch a character giving the
Python architecture, i.e. "32bit" or "64bit". useCstdout a logical
indicating if the C stdout should be used or the stout should be
redirected at a Python level.

TL; DR

Use pythonExePath to specify the python exe location and give it a go. Try subsequent parameters if things still don't work