util

Common utility (static) functions.

yael.util.VP_PATTERN_HW = <_sre.SRE_Pattern object at 0x24d7a30>

pattern to match viewport value height=H, width=W

yael.util.VP_PATTERN_WH = <_sre.SRE_Pattern object at 0x24d7f40>

pattern to match viewport value width=W, height=H

yael.util.clip_time_seconds(string)

Convert the given clip time string in seconds (possibly with decimal digits).

Parameters:string (str) – the clip time string to be converted Returns:the clip time in seconds Return type:float

yael.util.directory_size(path)

Compute the total size, in bytes, of all the files in the filesystem tree rooted at the given directory.

Parameters:path (str) – the path of the root directory Returns:the total size in bytes of the subtree rooted at path Type:integer

yael.util.is_valid(obj, allowed_class, single=True)

If single is True, return True if obj is an instance of allowed_class or None.

If single is False, return True if obj is a list (possibly, empty) of instances of allowed_class.

Parameters:

• obj (object or list) – the object to be checked
• allowed_class (class) – the allowed class
• single (bool) – if True, obj must be a single object

Returns:

whether the given object is valid

Return type:

bool

yael.util.list_all_files(path)

List all files in the filesystem tree rooted at the given directory.

Parameters:path (str) – the path to the root directory Returns:the list of files in the subtree rooted at path Type:list of str

yael.util.norm_join(path1, path2)

Join the two given paths and normalize the result.

Parameters:

• path1 (str) – prefix path
• path2 (str) – suffix path

Returns:

the join of the two paths, normalized

Return type:

str

yael.util.norm_join_parent(path1, path2)

Join the parent directory of path1 with path2 and normalize the result.

Parameters:

• path1 (str) – prefix path
• path2 (str) – suffix path

Returns:

the join of the parent directory of path1 with path2, and normalize (e.g., “a/../b/c” => “b/c”) the result

Return type:

str

yael.util.obfuscate_data(data, key, algorithm)

Obfuscate/deobfuscate data with the given key and algorithm.

Parameters:

• data (bytes) – the data to be obfuscated/deobfuscated
• key (str) – the string to be used as the obfuscation key
• algorithm (str) – the algorithm to be used (“adobe” or “idpf”)

Return type:

bytes

yael.util.parse_viewport_string(string)

Parse the given viewport value and return the corresponding dictionary {“width”: W, “height”: H}.

Parameters:string (str) – a viewport value Returns:{“width”: W, “height”: H} or None if string is not valid Return type:dict

yael.util.query_xpath(obj, query, args, nsp, required=None, formatted_query=None)

Perform an xpath query on an XML (lxml) node obj.

The query template will be formatted using args and the namespaces nsp. (This works only in Python 2.6+.)

If required is not None and the result is empty, raise an exception.

If formatted_query is passed, use it instead of formatting query with args. (Useful if working in Python <2.6.)

Parameters:

• obj (object) – the XML (lxml) node object
• query (str) – a string template to be formatted with args
• args (list of str) – a list of arguments to format the query
• nsp (dict) – namespace dictionary, mapping prefixes to namespace strings
• required (str) – required element
• formatted_query (str) – a pre-formatted query

Returns:

the matched XML node objects

Return type:

list of object

yael.util.safe_first(lis)

Return the first element of the list, dealing safely with None or empty arguments.

Parameters:lis (list of object) – a list of objects or values Returns:the first element of the list (or None if lis is None or empty) Return type:object or value

yael.util.safe_len(lis)

Return the number of elements of the list, dealing safely with non-list arguments.

Parameters:lis (list of object) – a list of objects or values Returns:the length of the list (or -1 if lis is not a list) Return type:int

yael.util.safe_strip(string)

Strip the given string, dealing safely with None arguments.

Parameters:string (str) – the string to be stripped Returns:the stripped string (or None if string is None) Return type:str

yael.util.split_reference(string)

Split the given reference (BASE#F) and return a dictionary {“base”: BASE, “fragment”: F}.

If there is no fragment, return {“base”: BASE}.

If the string is None, return {}.

Parameters:string (str) – a reference Returns:a dictionary containing base and fragment id Return type:dict