Improve type annotations

relational/relation.py

@@ -22,7 +22,8 @@
 import csv
 from itertools import chain, repeat
 from collections import deque
-from typing import List, Union, Set
+from typing import *
+from pathlib import Path
 
 from relational.rtypes import *
 
@@ -53,11 +54,11 @@ class Relation:
     '''
     __hash__ = None #  type: None
 
-    def __init__(self, filename: str = '') -> None:
+    def __init__(self, filename: Optional[Union[str, Path]] = None) -> None:
         self._readonly = False
         self.content: Set[tuple] = set()
 
-        if len(filename) == 0:  # Empty relation
+        if filename is None:  # Empty relation
             self.header = Header([])
             return
         with open(filename) as fp:
@@ -73,7 +74,7 @@ class Relation:
         self._readonly = True
         copy._readonly = True
 
-    def _make_writable(self, copy_content : bool = True) -> None:
+    def _make_writable(self, copy_content: bool = True) -> None:
         '''If this relation is marked as readonly, this
         method will copy the content to make it writable too
 
@@ -92,7 +93,7 @@ class Relation:
     def __contains__(self, key):
         return key in self.content
 
-    def save(self, filename: str) -> None:
+    def save(self, filename: Union[Path, str]) -> None:
         '''
         Saves the relation in a file. Will save using the csv
         format as defined in RFC4180.
@@ -169,7 +170,7 @@ class Relation:
                 newt.content.add(i + j)
         return newt
 
-    def projection(self, * attributes) -> 'Relation':
+    def projection(self, *attributes) -> 'Relation':
         '''
         Can be called in two different ways:
         a.projection('field1','field2')
@@ -200,7 +201,7 @@ class Relation:
             newt.content.add(tuple(row))
         return newt
 
-    def rename(self, params: 'Relation') -> 'Relation':
+    def rename(self, params: Dict[str, str]) -> 'Relation':
         '''
         Takes a dictionary.
 
@@ -505,7 +506,7 @@ class Header(tuple):
     def __repr__(self):
         return "Header(%s)" % super(Header, self).__repr__()
 
-    def rename(self, params) -> 'Header':
+    def rename(self, params: Dict[str, str]) -> 'Header':
         '''Returns a new header, with renamed fields.
 
         params is a dictionary of {old:new} names
@@ -525,15 +526,15 @@ class Header(tuple):
         '''Returns how many attributes this header has in common with a given one'''
         return len(set(self).intersection(set(other)))
 
-    def union(self, other) -> set:
+    def union(self, other: 'Header') -> Set[str]:
         '''Returns the union of the sets of attributes with another header.'''
         return set(self).union(set(other))
 
-    def intersection(self, other) -> set:
+    def intersection(self, other: 'Header') -> Set[str]:
         '''Returns the set of common attributes with another header.'''
         return set(self).intersection(set(other))
 
-    def getAttributesId(self, param) -> List[int]:
+    def getAttributesId(self, param: Iterable[str]) -> List[int]:
         '''Returns a list with numeric index corresponding to field's name'''
         try:
             return [self.index(i) for i in param]