pds4_tools.utils.helpers module

Functions

cast_int_float_string(value)	Cast given string value, if possible, to an int, float or returns unchanged.
is_array_like(value)	Array-like values are defined as those that implement __len__ (such as list, tuple, array.array, np.ndarray, etc) but are not str, unicode or bytes.
finite_min_max(array_like)	Obtain finite (non-NaN, non-Inf) minimum and maximum of an array.
dict_extract(nested_dict, key)	Recursively searches nested dictionaries.
xml_to_dict(xml_element[, skip_attributes, ...])	Transforms XML to an OrderedDict.

Details

cast_int_float_string(value)

Cast given string value, if possible, to an int, float or returns unchanged.

Parameters:

value : str or unicode

Value to try casting to an int and float.

Returns:

int, float, str or unicode

Cast value.

is_array_like(value)

Array-like values are defined as those that implement __len__ (such as list, tuple, array.array, np.ndarray, etc) but are not str, unicode or bytes.

Parameters:

value

Any kind of value.

Returns:

bool

True if value is array-like, false otherwise.

finite_min_max(array_like)

Obtain finite (non-NaN, non-Inf) minimum and maximum of an array.

Parameters:

array_like : array_like

A numeric array of some kind, possibly containing NaN or Inf values.

Returns:

tuple

Two-valued tuple containing the finite minimum and maximum of array_like.

dict_extract(nested_dict, key)

Recursively searches nested dictionaries.

nested_dict may contain other dictionaries, or other array-like’s that have dictionaries inside: all dictionaries anywhere will be searched.

Adapted from http://stackoverflow.com/a/29652561.

Parameters:

nested_dict : dict or OrderedDict

A dictionary potentially containing an arbitrary number of other dictionaries.

key : str or unicode

The key to search for in nested_dict.

Returns:

generator

Found values for key in any dictionary inside nested_dict.

Notes

This code is generally efficient. However, if you pass it a dictionary that has a huge array nested within it, it will not be performant because it will try to search each value in the array for a dictionary (this is by design; the intent if non-dict array-like’s are present is to search them on the assumption they will be small where using this function makes sense).

Examples

>>> d = { "id" : "abcde",
          "key1" : "blah",
          "key2" : "blah blah",
          "nestedlist" : [
            "blah blah",
            { "id" : "qwerty",
            "key1": "blah"} ]
        }
>>> result = dict_extract(d, 'id')

>>> print(list(result))
['abcde', 'qwerty']

xml_to_dict(xml_element, skip_attributes=False, cast_values=False, cast_ignore=(), tag_modify=())

Transforms XML to an OrderedDict.

Takes an XML ElementTree Element or a Label and creates an equivalent OrderedDict. Keys of the dictionary represent tag names and values represent the text values of the elements. In case of a (sub)element having child elements, values will be another OrderedDict, inside which the text of the element has key ‘_text’. In case of (sub)elements having child elements with the same key, the value for the key will be a list. In case of (sub)elements with attributes, the value will be an OrderedDict, inside which the key for each attribute starts with ‘@’ and the text of the element has key ‘_text’. For text elements, the text value is not preserved (and a ‘_text’ key is not created) if it contains only whitespace (including spaces, tabs and newlines); otherwise whitespaces are preserved.

Preserves order of elements in most cases. The exception is when an element has 2 or more sets of children, where each set has the same key names (i.e., there are at least 4 children, and 2 of those children have one key, and 2 have another key) and the order of the children with the non-matching keys is intertwined, in such a case the order of the intertwined keys will not be preserved.

Adapted from http://stackoverflow.com/a/10076823.

Parameters:

xml_element : ElementTree Element or Label

XML representation which will be turned into a dictionary.

skip_attributes : bool, optional

If True, skips adding attributes from XML. Defaults to False.

cast_values : bool, optional

If True, float and int compatible values of element text and attribute values will be cast as such in the output dictionary. Defaults to False.

cast_ignore : tuple[str or unicode], optional

If given, then a tuple of element tags and/or attribute names. If cast_values is True, then for elements and attributes matching exactly the values in this tuple, values will not be cast. Attribute names must be prepended by an ‘@’. If tag_modify is set, then tags and attribute names specified by cast_ignore should be the already tag modified versions. Empty by default.

tag_modify : tuple, optional

If given, then a 2-valued tuple with str or unicode values, or a tuple of 2-valued tuples. Any match, including partial, in element tag names and/or attributes names for each tag_modify[0] is replaced with tag_modify[1]. Empty by default.

Returns:

OrderedDict

Dictionary representation of the XML input.