Find all occurrences of for ... else

find_for_else.py

import ast
from pathlib import Path

class Visitor(ast.NodeVisitor):
    def __init__(self):
        self.for_found = 0
        self.for_else_found = 0
        self.while_found = 0
        self.while_else_found = 0
        self.files_tried = 0
        self.files_skipped = 0
    def visit_For(self, node):
        self.for_found += 1
        if node.orelse:
            self.for_else_found += 1
        self.generic_visit(node)
    def visit_While(self, node):
        self.while_found += 1
        if node.orelse:
            self.while_else_found += 1
        self.generic_visit(node)


def visit_file(file: Path, visitor: Visitor):
    try:
        module = ast.parse(file.read_text(encoding='utf-8'))
    except Exception:
        visitor.files_skipped += 1
        return
    visitor.files_tried += 1
    visitor.visit(module)

def visit_all(directory: Path, visitor: Visitor):
    for file in directory.rglob('*.py'):
        visit_file(file, visitor)

if __name__ == '__main__':
    visitor = Visitor()
    visit_all(Path.cwd(), visitor)
    print('for loops', visitor.for_found)
    print('for elses', visitor.for_else_found, f'({visitor.for_else_found / visitor.for_found:.2%})')
    print('while loops', visitor.while_found)
    print('while elses', visitor.while_else_found, f'({visitor.while_else_found / visitor.while_found:.2%})')
    print('# modules', visitor.files_tried)
    print('# skipped', visitor.files_skipped)

Results in various codebases and collections of projects:

for loops 1815
for elses 60 (3.31%)
while loops 347
while elses 4 (1.15%)
# modules 598
# skipped 2

for loops 140
for elses 3 (2.14%)
while loops 35
while elses 0 (0.00%)
# modules 112
# skipped 3

Well written script!

While on the topic, there is also try/except/else, which could even also be used here:

def visit_file(file: Path, visitor: Visitor):
    try:
        module = ast.parse(file.read_text(encoding='utf-8'))
    except Exception:
        visitor.files_skipped += 1
    else:
        visitor.files_tried += 1
        visitor.visit(module)

I know this is an old gist, but just thought it's relevant in a funny way and wanted to share.