Why cannot Julia v1.4 find the installed Python?

[fhkm]

1. I installed Python V3.8 on windows 7 x64 and would like to rebuild PyCall.
2. I added PyCall package.
3. I changed the global variable ENV

ENV[“PYTHON”] = “D:\programs\python\v38\python.exe”

4. Then I use the command

using Pkg;Pkg.build(“PyCall”)

I got the following error. Julia v1.4 cannot find Python v3.8 I have installed on the folder, although I set the global variable ENV.

julia> using Pkg;Pkg.build("PyCall")
   Building Conda ─→ `C:\Users\a225\.julia\packages\Conda\3rPhK\deps\bui
ld.log`
   Building PyCall → `C:\Users\a225\.julia\packages\PyCall\zqDXB\deps\bui
ld.log`
┌ Error: Error building `PyCall`:
│ ┌ Info: No system-wide Python was found; got the following error:
│ │ ErrorException("D:\\programs\\python\\v38\\python.exe is 32-bit, but
 Julia is 64-bit")
│ └ using the Python distribution in the Conda package
│ [ Info: Downloading miniconda installer ...
│ ERROR: LoadError: failed process: Process(`'C:\Windows\System32\Windows
PowerShell\v1.0\powershell.exe' -Version 3 -NoProfile -Command "[System.Net.ServicePointManager]::SecurityProtocol = [System.Net.SecurityProtocolType]::Tls12; (New-Object System.Net.Webclient).DownloadFile('https://repo.continuum.io/miniconda/Miniconda3-latest-Windows-x86_64.exe', 'C:\Users\a225\.julia\conda\3\installer.exe')"`, ProcessExited(3221225477)) [3221225477]
│ 
│ Stacktrace:
│  [1] pipeline_error at .\process.jl:525 [inlined]
│  [2] download_powershell(::String, ::String) at .\download.jl:20
│  [3] download at .\download.jl:64 [inlined]
│  [4] _install_conda(::String, ::Bool) at C:\Users\a225\.julia\packages\
Conda\3rPhK\src\Conda.jl:164
│  [5] _install_conda(::String) at C:\Users\a225\.julia\packages\Conda\3r
PhK\src\Conda.jl:155
│  [6] runconda(::Cmd, ::String) at C:\Users\a225\.julia\packages\Conda\3
rPhK\src\Conda.jl:112
│  [7] add(::String, ::String; channel::String) at C:\Users\a225\.julia\p
ackages\Conda\3rPhK\src\Conda.jl:188
│  [8] add at C:\Users\a225\.julia\packages\Conda\3rPhK\src\Conda.jl:187
[inlined] (repeats 2 times)
│  [9] top-level scope at C:\Users\a225\.julia\packages\PyCall\zqDXB\deps
\build.jl:84
│  [10] include(::String) at .\client.jl:439
│  [11] top-level scope at none:5
│ in expression starting at C:\Users\a225\.julia\packages\PyCall\zqDXB\de
ps\build.jl:43
└ @ Pkg.Operations D:\buildbot\worker\package_win64\build\usr\share\julia
\stdlib\v1.4\Pkg\src\Operations.jl:892