Robustness and strict=False
PDF is specified in various versions. The specification of PDF 1.7 has 978 pages. This length makes it hard to get everything right. As a consequence, a lot of PDF files are not strictly following the specification.
If a PDF file does not follow the specification, it is not always possible to be certain what the intended effect would be. Think of the following broken Python code as an example:
function (foo, bar):
# Potentially intended:
def function(foo, bar):
# Also possible:
function = (foo, bar)
Writing a parser you can go two paths: Either you try to be forgiving and try to figure out what the user intended, or you are strict and just tell the user that they should fix their stuff.
pypdf gives you the option to be strict or not.
pypdf has three core objects and all of them have a
strict=True means that pypdf will raise an exception if a PDF does
not follow the specification.
strict=False means that pypdf will try to be forgiving and do
something reasonable, but it will log a warning message. It is a best-effort