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Does python pip have the equivalent of node's package.json?

In NodeJS's npm you can create a package.json file to track your project dependencies. When you want to install them you just run npm install and it looks at your package file and installs them all with that single command.
When distributing my code, does python have an equivalent concept or do I need to tell people in my README to install each dependency like so:
pip install package1
pip install package2
Before they can use my code?

Once all necessary packages are added
pip freeze > requirements.txt
creates a requirement file.
pip install -r requirements.txt
installs those packages again, say during production.

The best way may be pipenv! I personally use it!
However in this guide i'll explain how to do it with just python and pip! And without pipenv! That's the first part! And it will give us a good understanding about how pipenv works! There is a second part that treat pipenv! Check the section pipenv (The more close to npm).
Python and pip
To get it all well with python! Here the main elements:
virtual environment
requirements file (listing of packages)
pip freeze command
How to install packages from a requirements file
Virtual environment and why
Note that for this the package venv is to be used! It's the official thing! And shiped with python 3 installation starting from 3.3+ !
To know well the what is it and the why check this out
https://docs.python.org/3/tutorial/venv.html
In short! A virtual environment will help us manage an isolated version of python interpreter! And so too installed packages! In this way! Different project will not have to depends on the same packages installation and have to conflict! Read the link above explain and show it well!
... This means it may not be possible for one Python installation to meet the requirements of every application. If application A needs version 1.0 of a particular module but application B needs version 2.0, then the requirements are in conflict and installing either version 1.0 or 2.0 will leave one application unable to run.
You may like to check the explanation on flask framework doc!
https://flask.palletsprojects.com/en/1.1.x/installation/#virtual-environments
Why we care about this and should use it! To isolate the projects! (each have it's environment)! And then freeze command will work per project base! Check the last section
Usage
Here a good guide on how to setup and work:
https://packaging.python.org/guides/installing-using-pip-and-virtual-environments/
Check the installation section first!
Then
To create a virtual environment you go to your project directory and run:
On macOS and Linux:
> python3 -m venv env
On Windows:
> py -m venv env
Note You should exclude your virtual environment directory from your version control system using .gitignore or similar.
To start using the environment in the console, you have to activate it
https://packaging.python.org/guides/installing-using-pip-and-virtual-environments/#activating-a-virtual-environment
On macOS and Linux:
> source env/bin/activate
On Windows:
> .\env\Scripts\activate
See the part on how you check that you are in the environment (using which (linux, unix) or where (windows)!
To deactivate you use
> deactivate
Requirement files
https://pip.pypa.io/en/latest/user_guide/#requirements-files
“Requirements files” are files containing a list of dependencies to be installed using pip install like so
(How to Install requirements files)
pip install -r requirements.txt
Requirements files are used to hold the result from pip freeze for the purpose of achieving repeatable installations. In this case, your requirement file contains a pinned version of everything that was installed when pip freeze was run.
python -m pip freeze > requirements.txt
python -m pip install -r requirements.txt
Some of the syntax:
pkg1
pkg2==2.1.0
pkg3>=1.0,<=2.0
== for precise!
requests==2.18.4
google-auth==1.1.0
Force pip to accept earlier versions
ProjectA
ProjectB<1.3
Using git with a tag (fixing a bug yourself and not waiting)
git+https://myvcs.com/some_dependency#sometag#egg=SomeDependency
Again check the link https://pip.pypa.io/en/latest/user_guide/#requirements-files
I picked all the examples from them! You should see the explanations! And details!
For the format details check: https://pip.pypa.io/en/latest/cli/pip_install/#requirements-file-format
Freeze command
Pip can export a list of all installed packages and their versions using the freeze comman! At the run of the command! The list of all installed packages in the current environment get listed!
pip freeze
Which will output something like:
cachetools==2.0.1
certifi==2017.7.27.1
chardet==3.0.4
google-auth==1.1.1
idna==2.6
pyasn1==0.3.6
pyasn1-modules==0.1.4
requests==2.18.4
rsa==3.4.2
six==1.11.0
urllib3==1.22
We can write that to a requirements file as such
pip freeze > requirements.txt
https://pip.pypa.io/en/latest/cli/pip_freeze/#pip-freeze
Installing packages Resume
By using venv (virtual environment) for each project! The projects are isolated! And then freeze command will list only the packages installed on that particular environmnent! Which make it by project bases! Freeze command make the listing of the packages at the time of it's run! With the exact versions matching! We generate a requirements file from it (requirements.txt)! Which we can add to a project repo! And have the dependencies installed!
The whole can be done in this sense:
Linux/unix
python3 -m venv env
source env/bin/activate
pip3 install -r requirements.txt
Windows
py -m venv env
.\env\Scripts\activate
pip3 install -r requirements.txt
First time setup after cloning a repo!
Creating the new env!
Then activating it!
Then installing the needed packages to it!
Otherwise here a complete guide about installing packages using requiremnets files and virtual environment from the official doc: https://packaging.python.org/guides/installing-using-pip-and-virtual-environments/
This second guide show all well too: https://docs.python.org/3/tutorial/venv.html
Links listing (already listed):
https://pip.pypa.io/en/latest/user_guide/#requirements-files
https://pip.pypa.io/en/latest/cli/pip_install/#requirements-file-format
https://pip.pypa.io/en/latest/cli/pip_freeze/#pip-freeze
pipenv (The more close to npm)
https://pipenv.pypa.io/en/latest/
pipenv is a tool that try to be like npm for python! Is a super set of pip!
pipenv create virtual environment for us! And manage the dependencies!
A good feature too is the ability to writie packages.json like files! With scripts section too in them!
Executing pipfile scripts
run python command with alias in command line like npm
Installation
https://pipenv.pypa.io/en/latest/install/
virtualenv-mapping-caveat
https://pipenv.pypa.io/en/latest/install/#virtualenv-mapping-caveat
For me having the env created within the project (just like node_modules) should be even the default! Make sure to activate it! By setting the environment variable!
pipenv can seems just more convenient!
Mainly managing run scripts is too good to miss on! And a one tool that simplify it all!
Basic usage and comparing to npm
https://pipenv.pypa.io/en/latest/basics/
(make sure to check the guide above to get familiar with the basics)
Note that the equivalent of npm package.json is the PipFile file!
An example:
[[source]]
url = "https://pypi.org/simple"
verify_ssl = true
name = "pypi"
[packages]
flask = "*"
simplejson = "*"
python-dotenv = "*"
[dev-packages]
watchdog = "*"
[scripts]
start = "python -m flask run"
[requires]
python_version = "3.9"
There is Pipfile.lock like package.lock
To run npm install equivalent! You run pipenv install!
To insall a new package
pipenv install <package>
This will create a Pipfile if one doesn’t exist. If one does exist, it will automatically be edited with the new package you provided.
Just like with npm!
$ pipenv install "requests>=1.4" # will install a version equal or larger than 1.4.0
$ pipenv install "requests<=2.13" # will install a version equal or lower than 2.13.0
$ pipenv install "requests>2.19" # will install 2.19.1 but not 2.19.0
If the PIPENV_VENV_IN_PROJECT=1 env variable is set! To make pipenv set the virtual environmnent within the project! Which is created in a directory named .venv (equiv to node_modules).
Also running pipenv install without a PipFile in the directory! Neither a virtual environment! Will create the virtual environment on .venv directory (node_modules equiv)! And generate a PipFile and Pipfile.lock!
Installing flask example:
pipenv install flask
Installing as dev dependency
pipenv install watchdog -d
or
pipenv install watchdog -dev
just like with npm!
pipenv all commands (pipenv -h)
Commands:
check Checks for PyUp Safety security vulnerabilities and against PEP
508 markers provided in Pipfile.
clean Uninstalls all packages not specified in Pipfile.lock.
graph Displays currently-installed dependency graph information.
install Installs provided packages and adds them to Pipfile, or (if no
packages are given), installs all packages from Pipfile.
lock Generates Pipfile.lock.
open View a given module in your editor.
run Spawns a command installed into the virtualenv.
scripts Lists scripts in current environment config.
shell Spawns a shell within the virtualenv.
sync Installs all packages specified in Pipfile.lock.
uninstall Uninstalls a provided package and removes it from Pipfile.
update Runs lock, then sync.
Command help
pipenv install -h
importing from requirements.txt
https://pipenv.pypa.io/en/latest/basics/#importing-from-requirements-txt
environment management with pipenv
https://pipenv.pypa.io/en/latest/basics/#environment-management-with-pipenv
pipenv run
To run anything with the project virtual environment you need to use pipenv run
As like pipenv run python server.py!
Custom scripts shortcuts
scripts in npm!
https://pipenv.pypa.io/en/latest/advanced/#custom-script-shortcuts
[scripts]
start = "python -m flask run"
And to run
pipenv run start
Just like with npm!
If you’d like a requirements.txt output of the lockfile, run $ pipenv lock -r. This will include all hashes, however (which is great!). To get a requirements.txt without hashes, use $ pipenv run pip freeze.
To mention too the pipenv cli rendering is well done:
Make sure to read the basics guide!
And you can see how rich is pipenv!

Yes, it's called the requirements file:
https://pip.pypa.io/en/stable/cli/pip_install/#requirement-specifiers
You can specify the package name & version number.
You can also specify a git url or a local path.
In the usual case, you would specify the package followed by the version number, e.g.
sqlalchemy=1.0.1
You can install all the packages specified in a requirements.txt file through the command
pip install -r requirements.txt

Once all the packages have been installed, run
pip freeze > requirements.txt
This will save the package details in the file requirements.txt.
For installation, run
pip install -r requirements.txt
to install the packages specified by requirements.txt.

I would like to propose pipenv here. Managing packages with Pipenv is easier as it manages the list and the versions of packages for you because I think you need to run pip freeze command each time you make changes to your packages.
It will need a Pipfile. This file will contain all of your required packages and their version just like package.json.
You can delete/update/add projects using pipenv install/uninstall/update <package>
This also generates a dependency tree for your project. Just like package-lock.json
Checkout this post on Pipfiles
Learn more about Pipenv

Installed Virtualenv and activating virtualenv doesn't work

I cloned my Django Project from Github Account and activated the virtualenv using famous command source nameofenv/bin/activate
And when I run python manage.py runserver
It gives me an error saying:
ImportError: Couldn't import Django. Are you sure it's installed and available on your PYTHONPATH environment variable? Did you forget to activate a virtual environment?

I was thinking that every and each dependency I need, might be present inside virtualenv.
Well, no. By default, a newly created virtualenv comes empty, that is, with no third-party library. (Optionaly, you may allow a virtualenv to access libraries installed system-wide, but that's another story.)
Once the virtualenv is created, you need to install the dependencies you need.
(How could virtualenv know what dependencies you need?)
The procedure is to install the virtualenv, activate it, and then install the libraries needed for the project (in you case Django and perhaps others).
If you project has a requirements.txt, you may install every required dependency with the command:
pip install -r requirements.txt
If your project has a setup.py, you may also execute
pip install -e path/to/your/project/clone/.
to install the project in the virtualenv. This should install the dependencies.
Of course, if the only dependency is Django, you can just type
pip install django

on ubuntu version
#install python pip
sudo apt-get install python-pip
#install python virtualenv
sudo apt-get install python-virtualenv
# create virtual env
virtualenv myenv
#activate the virtualenv
. myenv/bin/activate
#install django inside virtualenv
pip install django
#create a new django project
django-admin.py startproject mysite
#enter to the folder of the new django project
cd mysite
#run the django project
python manage.py runserver

If you have several python on your machine, for example,python2.7, python3.4, python3.6, it is import to figure out which version the python really reference to, and more over, which version does pip reference to.
The same problem got in my way after I installed the let's encrypt when I run the following command.
(python3 manage.py runserver 0:8000 &)
I inspected the python version and found that python3, python3.4, python3.6, python3.4m were all available.
I just change python3 to python3.6 and solved the problem.
(python3.6 manage.py runserver 0:8000 &)
So, this is probably a version mismatching problem if it is OK for a long time and crashes down suddenly.

I'm guessing you also upload the virtual environment from your other pc. And you hope that only activating that will work, bzz.
It's not recommended to upload the virtualenv files to your git repository, as #Alain says it's a good practice to have a requirements.txt file containing the project dependencies. You can use pip freeze > requirements.txt (when the environment is activated) to generate the project requirements file.
By doing so, when you clone the repository from another computer, you need to create a new virtualenv by issuing the command:
virtualenv nameofenv
then activate it:
source nameofenv/bin/activate
and finally, use the requirements file to install the requirements for your project using:
pip install -r requirements.txt

I had installed Django 2 via pip3 install Django, but I was running python manage.py runserver instead of python3 manage.py runserver. Django 2 only works with python 3+.

Global installations - Flask & Python

How can I tell if flask or python are installed globally? Everytime I attempt to push a flask python app locally I need to copy the flask, jinja2, markupsafe,and werkzeug directories along with file itsdangerous.py
I have had a little experience with paths before, as such I did the echo $PATH command and received my path
/home/me/rampup/webapp/venv/bin:/usr/local/heroku/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
Should I append my $PATH with the path locations of python and flask? If so how would I identify the paths of those applications?

You probably don't want to manually copy your dependencies around. (It's tedious and error prone). Instead, install pip (to manage your dependencies) and virtualenv[1] (to allow you to work on multiple projects with conflicting dependencies). Then:
Create a virtual environment: virtualenv venv
Activate said virtual environment . venv/bin/activate
Use pip to install your dependencies pip install Flask
There is no step #4
For deployments, simply ask pip to produce a manifest of all the dependencies you have with the command pip freeze (you can redirect it to a requirements.txt file with the following command pip freeze > requirements.txt). Then you can install the same dependencies with pip install -r requirements.txt on the remote machine.
[1]: If you are on Python 3.4+ you already have both - although you'll use pyvenv-3.4 instead of virtualenv.

How to clone a django reporsitory into a virtualenv

I've got a virtualenv set up for a django app. So far I've installed all my packages via pip when the virtualenv is activated, but I now need to clone one from bitbucket. Is there a special way to do this or do I just need to open a terminal, goto venv/lib/python2.7/site-packages and run the clone command?
Here's the repository i'm trying to clone https://bitbucket.org/basti/python-amazon-product-api/src

Use the -e flag and specify a git repo:
pip install -e git://github.com/manojlds/mylib.git#egg=mylib
The url above can be bitbucket, github etc.
-e, --editable <VCS+REPOS_URL[#REV]#EGG=PACKAGE>
Install a package directly from a checkout. Source will be checked
out into src/PACKAGE (lower-case) and installed in-place (using
setup.py develop). You can run this on an existing directory/checkout
(like pip install -e src/mycheckout). This option may be provided
multiple times. Possible values for VCS are: svn, git, hg and bzr.

clone repository,
if your app is has setup.py, then run python setup.py install
when virtual env is actived.
else copy this app inside you django project and add name of it your INSTALLED_APPS in settings.py
or you can use pip install -e <repo_addr>, see doc.

How to install Django using source code in virtual environment?

My environment is in /home/karan/envs/ and is called env1. My working directory is /home/karan/ and django is on the desktop.
How can I install django in my environment using the local copy? Please tell me where I should cd so the installation is smooth.
Will sudo python setup.py install when the environment is activated work? Can that change my system files?

You can do it like this:
First Activate your virtual environment
cd into the project folder
then do python setup.py install
FYI you can use pip to install django.
pip install Django

The best way to start with a django project is keep all your requirements inside requirements.txt file. Then install it from pip.
For ex:- create a text file with the name as requirements.txt.
Inside that write all your requirements as below
Django==1.4
MySQL-python==1.2.3
ipython==0.13
Then save it.
Activate your env using this command: source test_env/bin/activate
Then use this command: pip install -r requirements.txt
It will install all your requirements inside the environment. Then you can run your project from env.
Hope this helps