CondaValueError: Value error: prefix already exists: - runtime-error

Question

Reference:
https://uoa-eresearch.github.io/eresearch-cookbook/recipe/2014/11/20/conda/
I've run the following commands to install conda and create a virtual environment. Continue reading after code block for my question.
C:\Windows\System32>conda -V
conda 4.1.11
C:\Windows\System32>conda update conda
Fetching package metadata .........
Solving package specifications: ..........
Package plan for installation in environment C:\Program Files\Miniconda2:
The following packages will be downloaded:
package | build
---------------------------|-----------------
conda-env-2.6.0 | 0 498 B
enum34-1.1.6 | py27_0 53 KB
conda-4.2.9 | py27_0 421 KB
------------------------------------------------------------
Total: 475 KB
The following NEW packages will be INSTALLED:
enum34: 1.1.6-py27_0
The following packages will be UPDATED:
conda: 4.1.11-py27_0 --> 4.2.9-py27_0
conda-env: 2.5.2-py27_0 --> 2.6.0-0
Proceed ([y]/n)? y
Fetching packages ...
conda-env-2.6. 100% |###############################| Time: 0:00:00 99.60 kB/s
enum34-1.1.6-p 100% |###############################| Time: 0:00:00 719.03 kB/s
conda-4.2.9-py 100% |###############################| Time: 0:00:00 1.33 MB/s
Extracting packages ...
[ COMPLETE ]|##################################################| 100%
Unlinking packages ...
[ COMPLETE ]|##################################################| 100%
Linking packages ...
[ COMPLETE ]|##################################################| 100%
C:\Windows\System32>
C:\Windows\System32>Python -V
Python 2.7.12
C:\Windows\System32>conda create -n ENV1 python=2.7.12 anaconda
...
<-- chose 'n' for install
I chose 'n' here, because this is when I crashed my Linux server because I ran out of disk space when a billion programs (give or take) were asked to be installed. Instead, I chose 'n', and then wanted to log this to a file so I could see the entire list because I couldn't scroll up in the Windows command prompt, so I ran the code below instead. It sat for a while, and then I broke out using CTRL+C. Continue reading after code block for my question.
C:\Windows\System32>conda create -n ENV1 python=2.7.12 anaconda > C:\output.txt
y
Traceback (most recent call last):
File "C:\Program Files\Miniconda2\Scripts\conda-script.py", line 5, in <module
>
sys.exit(conda.cli.main())
File "C:\Program Files\Miniconda2\lib\site-packages\conda\cli\main.py", line 1
50, in main
return conda_exception_handler(_main)
File "C:\Program Files\Miniconda2\lib\site-packages\conda\exceptions.py", line
473, in conda_exception_handler
return_value = func(*args, **kwargs)
File "C:\Program Files\Miniconda2\lib\site-packages\conda\cli\main.py", line 1
44, in _main
exit_code = args.func(args, p)
File "C:\Program Files\Miniconda2\lib\site-packages\conda\cli\main_create.py",
line 68, in execute
install(args, parser, 'create')
File "C:\Program Files\Miniconda2\lib\site-packages\conda\cli\install.py", lin
e 405, in install
execute_actions(actions, index, verbose=not context.quiet)
File "C:\Program Files\Miniconda2\lib\site-packages\conda\plan.py", line 643,
in execute_actions
inst.execute_instructions(plan, index, verbose)
File "C:\Program Files\Miniconda2\lib\site-packages\conda\instructions.py", li
ne 134, in execute_instructions
cmd(state, arg)
File "C:\Program Files\Miniconda2\lib\site-packages\conda\instructions.py", li
ne 47, in FETCH_CMD
fetch_pkg(state['index'][arg + '.tar.bz2'])
File "C:\Program Files\Miniconda2\lib\site-packages\conda\fetch.py", line 336,
in fetch_pkg
download(url, path, session=session, md5=info['md5'], urlstxt=True)
File "C:\Program Files\Miniconda2\lib\site-packages\conda\fetch.py", line 419,
in download
for chunk in resp.iter_content(2**14):
File "C:\Program Files\Miniconda2\lib\site-packages\requests\models.py", line
664, in generate
for chunk in self.raw.stream(chunk_size, decode_content=True):
File "C:\Program Files\Miniconda2\lib\site-packages\requests\packages\urllib3\
response.py", line 353, in stream
data = self.read(amt=amt, decode_content=decode_content)
File "C:\Program Files\Miniconda2\lib\site-packages\requests\packages\urllib3\
response.py", line 310, in read
data = self._fp.read(amt)
File "C:\Program Files\Miniconda2\lib\httplib.py", line 612, in read
s = self.fp.read(amt)
File "C:\Program Files\Miniconda2\lib\socket.py", line 384, in read
data = self._sock.recv(left)
File "C:\Program Files\Miniconda2\lib\ssl.py", line 756, in recv
return self.read(buflen)
File "C:\Program Files\Miniconda2\lib\ssl.py", line 643, in read
v = self._sslobj.read(len)
KeyboardInterrupt
C:\Windows\System32>conda create -n ENV1 python=2.7.12 anaconda > C:\output.txt
CondaValueError: Value error: prefix already exists: C:\Program Files\Miniconda2
\envs\ENV1
How can I remove the ENV1 prefix so I can try re-installing? And how can I log all of this output in Windows. The input is not visible if I move to C:\output.txt.

Answer 1

I simply deleted folder C:\Program Files\Miniconda2\envs\ENV1\.

Answer 2

You can overwrite the existing enviroment by adding the --force option.
So:
conda create -n ENV1 python=2.7.12 anaconda --force
Make sure that you have updated you anaconda because it is a recent function.
Edit: --force feature was added in conda 4.6, but apparently on latest versions 4.7, 4.8, it doesn't always work

Answer 3

When the conda environment was previously removed, but the actual directory still exists (for some reason), then the "conda env remove -n ENV1" will do nothing:
$ conda-env list
# conda environments:
#
base * /home/nmanos/miniconda
test-env /home/nmanos/miniconda/envs/test-env
$ conda-env remove -n ENV1
# Nothing was removed (exit code zero)
$ ls /home/nmanos/miniconda/envs/ENV1
bin conda-meta etc go
# Directory still exists
So you can remove the actual ENV1 directory, as follow:
$ ENV_BASE=$(conda-env list | awk '/base/ { print $NF }')
$ echo $ENV_BASE
/home/nmanos/miniconda
$ rm -rf "$ENV_BASE/envs/ENV1"

Answer 4

You can just deactivate the existing one and remove it and then create the new one.
conda deactivate
conda env remove -n env_name

Answer 5

Open your environment.yml file
Check the name and prefix of the environment, usually at the first line (name) and the last line (prefix) of the file.
Rename both the name and prefix path to whatever name you are trying to create the new environment.
Run the create env command again.
conda env list should give your new environment now.
It is most likely that you are having the name (& prefix) of the other env which is already existing from where you got the environment.yml.

Answer 6

The next time you open the terminal and the prompt is
(base) C:\Users\whatever>
Just type:
(base) C:\Users\whatever> conda activate ENV1
Your prompt should change to:
(ENV1) C:\Users\whatever>
And once your work is done just say:
(ENV1) C:\Users\whatever> conda deactivate
Because it's obviously inconvenient to keep deleting the folder over and over