Prerequisites

1. You need to have a CDS or ADS account. If you don't have an account, please self register at the CDS registration page or the ADS registration, whichever is appropriate.
2. You need Python

   • Option 1: use Python 2.

     If you want to use Python 2, then it should come with your macOS. Open a Terminal and type command 'python'. You should see something like 'Python 2.7.10 (default, Feb 22 2019, 21:17:52)'. Type 'Control + D' to quit. For Python 2, run the 2 commands below to install pip: curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py python get-pip.py

     
     

   • Option 2: use Python 3. You are recommended to follow instructions here using Homebrew.xcode-select --install

     xcode-select --install /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)" brew install python3

     
     

3. Optional: you are recommended to set up a virtual environment.

Python 3 comes up with this feature. For Python 2, you may want to use Virtualenv. This is out of the scope of this knowledge base article.

Step-by-step guide

1. Login to CDS (or Login to ADS)
2. Copy a 2 line code, which shows a url and your own uid:API key details as follows:
   1. For CDS users, Go to this page and copy the 2 line code displayed in the black box in the "Install the CDS API key" section.
   2. For ADS users, Go to this page and copy the 2 line code displayed in the black box in the "Install the CDS API key" section.

3. Create your key file in your home directory in your Terminal window as follows:

   touch ~/.cdsapirc

   
   

4. Edit your key file and paste the two lines you copied in Step 2 above to your .cdsapirc key file.

5. Install the CDS API client using pip, by running the following command in your Terminal window:

   pip install cdsapi

   
   

6. Once the CDS API client is installed, it can be used to request data from the datasets listed in the CDS and ADS catalogues. It is necessary to agree to the Terms of Use of every datasets that you intend to download. Attached to each dataset download form, the 'Show API request' button displays the python code to be used.

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