Create PEEP-006.md

[xoelop]

PEEP to add the option to save exact libraries versions to Pipfile

Thank you for contributing to Pipenv!

The issue

As described in #3441, it would be interesting if when installing a certain package with pipenv without specifying the version (pipenv install scipy, for example), there was a flag that saved the exact version that was installed to the Pipfile. Something like the --save-exact flag in npm.

The fix

Right now this can be accomplished, AFAIK, manually editing the version numbers in Pipfile, but it's quite annoying.

The checklist

• [ YES] Associated issue: 'save-exact' option for saving exact version in Pipfile #3441
• A news fragment in the news/ directory to describe this fix with the extension .bugfix, .feature, .behavior, .doc. .vendor. or .trivial (this will appear in the release changelog). Use semantic line breaks and name the file after the issue number or the PR #.

[hoshsadiq]

This already exists:

$ pipenv install scipy==1.2.0
<clipped>
$ cat Pipfile
[[source]]
name = "pypi"
url = "https://pypi.org/simple"
verify_ssl = true

[dev-packages]

[packages]
scipy = "==1.2.0"

[requires]
python_version = "3.6"

pipenv accepts any version that pip can accept when it comes to version constraints.

[xoelop]

I've just edited the PR so that it's clearer to see what I meant.

I know you can specify a version to pipenv like that, but that adds an extra step of looking what is the latest available version for every package you want to install. Plus there may be libraries whose latest versions aren't compatible, a problem you wouldn't run into just doing pipenv install scipy only, and letting pipenv figure out the latest versions of all the necessary dependencies.

Ideally, one would be able to save the exact versions to pipfile, without specifying those versions but saving the ones currently installed, so that other people can install them as well

Those versions are saved in pipfile.lock. Is there any way to install all the libraries from pipfile.lock instead of from pipfile?

EDIT: just saw that it's possible to install from pipfile.lock, ignoring pipfile. Flag --ignore-pipfile. Source: https://pipenv-es.readthedocs.io/es/latest/basics.html#pipenv-install

This solves my problem, I think this PR could be closed as it's not necessary anymore