create the validations

validate.py

+""" Defines validators or functions that create validators.
+A validator is a function that when applied to data returns
+a list of detected problems or an empty list otherwise.
+The list pattern is used to enable validator composition."""
+
+from util.seqs import seq_not_str, join
+from util import stats
+
+
+prob = stats.validate_probability
+
+
+def verify(validator, data):
+    """Asserts data via validator."""
+    result = validator(data)
+    assert not result, f'{result}'
+
+
+def values(validator_dict):
+    """ Creates validator applying provided validators to data of same keys
+    :param validator_dict: dictionary of functions """
+
+    assert isinstance(validator_dict, dict)
+
+    return lambda data_dict:\
+        join(validator_dict[k](data_dict[k]) for k in validator_dict.keys())
+
+
+def seq(f, n=0):
+    """Creates validator applying f to all elements of an iterable (but not a string)."""
+
+    def seq_validator(objs):
+        """Function returned"""
+        if not seq_not_str(objs):
+            return [f'Sequence expected: {objs}']
+        if n and n != len(objs):
+            return [f'Not of length {n}: {objs}']
+        return join(map(f, objs))
+
+    return seq_validator
+
+
+def cls(typ):
+    """ Returns validator if input is an instance of cls."""
+    return lambda obj: [] if isinstance(obj, typ) \
+        else [f'{obj} not an instance of {typ}']
+
+
+def aligned(seqs):
+    """Validates if all elements of seqs have equal length"""
+    return [] if len(set(len(i) for i in seqs)) == 1 else [f'Different lengths: {seqs}']
+
+
+def same(objs):
+    """ If all are equal. """
+    return [] if len(set(objs)) == 1 else [f'Not equal: {objs}']
+
+
+def counter(n):
+    """If n is non-negative int """
+    return [] if isinstance(n, int) and (n >= 0) else [f'Not a positive integer: {n}']
+
+
+def size(n):
+    """Creates validator if iterable has length n"""
+    return lambda seq: [] if len(seq) == n else [f'Length not {n}: {seq}']
+
+
+def both(left, right):
+    """Creates validator collecting results from two other validators."""
+    return lambda obj: join((left(obj), right(obj)))
\ No newline at end of file