use pip --pre option to install pre-release

README.md

@@ -41,7 +41,7 @@ python -m venv env
 source env/bin/activate
 
 # install from nplinker releases (requiring ~300MB of disk space)
-pip install nplinker==2.0.0a2
+pip install --pre nplinker
 
 # or install the latest from source code
 pip install git+https://github.com/nplinker/nplinker@dev 

docs/install.md

@@ -16,17 +16,18 @@ python --version
 
 # Create a new virtual environment
 python -m venv env          # (1)!
-source env/bin/activate
+source env/bin/activate     # (2)! 
 
 # install nplinker package (requiring ~300MB of disk space)
-pip install nplinker==2.0.0a2 # (2)! 
+pip install --pre nplinker # (3)!
 
 # install nplinker non-pypi dependencies and databases (~4GB)
 install-nplinker-deps
 ```
 
 1. A virtual environment is ***required*** to install the the non-pypi dependencies. You can also use `conda` to create a new environment. But NPLinker is not available on conda yet.
-2. NPLinker v2 is still under development and released as [pre-release](https://pypi.org/project/nplinker/#history). To install the pre-release, you have to explicitly specifiy the version. The command `pip install nplinker` will install the legacy NPLinker (v1.3.2), which is not recommended. 
+2. Check `pip` command and make sure it is provided by the activated virtual environment. 
+3. NPLinker v2 is still under development and released as [pre-release](https://pypi.org/project/nplinker/#history). To install the pre-release, you need the `--pre` option. 
 
 ## Install from source code