Use:
pip install -r requirements.txt
For further details, please check the help option:
pip install --help
We can find the option '-r' -
-r, --requirement Install from the given requirements file. This option can be used multiple times.
Further information on some commonly used pip install options (this is the help option on the pip install command):
Also the above is the complete set of options. Please use pip install --help
for the complete list of options.