1.3. Boolean Connectives

Both leader matcher and field matcher can be combined in any order using the Boolean connectives conjunction && and disjunction ||. The && operator has higher precedence than the || operator, which may require parentheses ((...)) to be used around sub-expressions.

>>> from marc21_learn.io import read_marc21
>>>
>>> filename = "../tests/data/ada.mrc"
>>>
>>> predicate = "ldr.type == 'z' \
...     && 005[0:4] == '2025' \
...     && 075{ b == 'piz' && 2 == 'gndspec' } \
...     && 042.a == 'gnd1' \
...     && 079.q == 's' \
... "
>>>
>>> df = read_marc21(filename, "001", predicate=predicate)
>>> assert df.height == 1