The minimal task to start any program environment is to print a simple message. The minimal interaction with an ICAT server is to connect to it and get its version. We'll combine both in a simple program:
.. literalinclude:: ../tutorial/hello.py
If you run this script, you should get something like the following as output:
$ python hello.py Connect to https://icat.example.com:8181 ICAT version 4.10
The constructor of :class:`icat.client.Client` takes the URL of the ICAT service as argument. It contacts the ICAT server, queries the version and stores the result to the attribute :attr:`~icat.client.Client.apiversion` of the client object. Obviously, you'll need to change the variable url in this example to point to your ICAT server.
If your ICAT server does not have a trusted SSL certificate you may get (depending on your Python version) an error instead:
$ python hello.py Traceback (most recent call last): ... urllib.error.URLError: <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:548)>
In this case, you may either install a trusted certificate in your
server now or modify your hello program and add a flag
checkCert=False to the constructor call like this:
.. literalinclude:: ../tutorial/hello-nocert.py
The future statement at the beginning of the example is only needed to compile print as a built-in function rather than a statement. We'll use it throughout the tutorial to ensure that the examples will work with Python 2 as well as with Python 3.
The class :class:`icat.client.Client` plays the central role in python-icat programs. Most of your code will deal with objects of this class. For this reason, the class is imported by default in the :mod:`icat` package. The above example could also be written as:
.. literalinclude:: ../tutorial/hello-client.py