Some cleanup for Python 3.7 and for succinctness

Author: davecom

Chapter1/fib1.py

@@ -13,6 +13,8 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+
+
 def fib1(n: int) -> int:
     return fib1(n - 1) + fib1(n - 2)
 

Chapter1/fib2.py

@@ -13,11 +13,14 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+
+
 def fib2(n: int) -> int:
     if n < 2:  # base case
         return n
     return fib2(n - 2) + fib2(n - 1)  # recursive case
 
+
 if __name__ == "__main__":
     print(fib2(5))
     print(fib2(10))

Chapter1/fib3.py

@@ -14,13 +14,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 from typing import Dict
-memo: Dict[int, int] = {0: 0, 1: 1}  # our old base cases
+memo: Dict[int, int] = {0: 0, 1: 1}  # our base cases
 
 
 def fib3(n: int) -> int:
-    if n in memo:  # our new base cases
-        return memo[n]
-    else:
+    if n not in memo:
         memo[n] = fib3(n - 1) + fib3(n - 2)  # memoization
     return memo[n]
 

Chapter1/trivial_compression.py

@@ -13,6 +13,8 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+
+
 class CompressedGene:
     def __init__(self, gene: str) -> None:
         self._compress(gene)

Chapter2/generic_search.py

@@ -13,6 +13,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from __future__ import annotations
 from typing import TypeVar, Iterable, Sequence, Generic, List, Callable, Set, Deque, Dict, Any, Optional
 from typing_extensions import Protocol
 from functools import total_ordering
@@ -81,13 +82,13 @@ def __repr__(self) -> str:
 
 
 class Node(Generic[T]):
-    def __init__(self, state: T, parent: Optional['Node'], cost: float = 0.0, heuristic: float = 0.0) -> None:
+    def __init__(self, state: T, parent: Optional[Node], cost: float = 0.0, heuristic: float = 0.0) -> None:
         self.state: T = state
-        self.parent: Optional['Node'] = parent
+        self.parent: Optional[Node] = parent
         self.cost: float = cost
         self.heuristic: float = heuristic
 
-    def __lt__(self, other: 'Node') -> bool:
+    def __lt__(self, other: Node) -> bool:
         return (self.cost + self.heuristic) < (other.cost + other.heuristic)
 
 

Chapter2/missionaries.py

@@ -13,6 +13,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from __future__ import annotations
 from typing import List, Optional
 from generic_search import bfs, Node, node_to_path
 
@@ -44,8 +45,8 @@ def is_legal(self) -> bool:
             return False
         return True
 
-    def successors(self) -> List["MCState"]:
-        sucs: List["MCState"] = []
+    def successors(self) -> List[MCState]:
+        sucs: List[MCState] = []
         if self.boat: # boat on west bank
             if self.wm > 1:
                 sucs.append(MCState(self.wm - 2, self.wc, not self.boat))
@@ -88,7 +89,7 @@ def display_solution(path: List[MCState]):
 
 
 if __name__ == "__main__":
-    start: MCState = MCState(3, 3, True)
+    start: MCState = MCState(MAX_NUM, MAX_NUM, True)
     solution: Optional[Node[MCState]] = bfs(start, MCState.goal_test, MCState.successors)
     if solution is None:
         print("No solution found!")

Chapter3/send_more_money.py

@@ -40,9 +40,7 @@ def satisfied(self, assignment: Dict[str, int]) -> bool:
             send: int = s * 1000 + e * 100 + n * 10 + d
             more: int = m * 1000 + o * 100 + r * 10 + e
             money: int = m * 10000 + o * 1000 + n * 100 + e * 10 + y
-            if send + more == money:
-                return True # answer found
-            return False # this full assignment doesn't work
+            return send + more == money
         return True # no conflict
 
 

Chapter3/word_search.py

@@ -15,6 +15,7 @@
 # limitations under the License.
 from typing import NamedTuple, List, Dict, Optional
 from random import choice
+from string import ascii_uppercase
 from csp import CSP, Constraint
 
 Grid = List[List[str]]  # type alias for grids
@@ -25,12 +26,9 @@ class GridLocation(NamedTuple):
     column: int
 
 
-ALPHABET: str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
-
-
 def generate_grid(rows: int, columns: int) -> Grid:
     # initialize grid with random letters
-    return [[choice(ALPHABET) for c in range(columns)] for r in range(rows)]
+    return [[choice(ascii_uppercase) for c in range(columns)] for r in range(rows)]
 
 
 def display_grid(grid: Grid) -> None:
@@ -70,9 +68,7 @@ def __init__(self, words: List[str]) -> None:
     def satisfied(self, assignment: Dict[str, List[GridLocation]]) -> bool:
         # if there are any duplicates grid locations then there is an overlap
         all_locations = [locs for values in assignment.values() for locs in values]
-        if len(set(all_locations)) < len(all_locations):
-            return False
-        return True
+        return len(set(all_locations)) == len(all_locations)
 
 
 if __name__ == "__main__":