Naive Use Case of Structural Pattern Matching (Python 3.10)

structural-pattern-matching.py

# https://www.python.org/dev/peps/pep-0634/
# PEP 634 proposed (and was accepted) Structural Pattern Matching (switch/case)
# for Python (available in 3.10) - as of this Gist,
# prerelease 3.10.0b2 is available

import inspect

F = [
  lambda x,y: x+y,
  lambda x: x+1,
  lambda x,y,z: x*y*z,
  lambda a,b,c,d: a+b+c+d,
]

_F = []

for f in F:
  match len(inspect.getfullargspec(f).args):
    case 1:
      print('This lambda has 1 arg - OK\n')
    case 2:
      print('This lambda has 2 arg - OK\n')
    case 3:
      print('This lambda has 3 arg - OK\n')
    case _:
      _F.append(f)
      F.remove(f)
      print('Error: Incorrect number of arguments found in lambda structure - FAIL\n')

_sources = ['\n' + str(inspect.getsource(_f)) for _f in _F]
sources = ['\n' + str(inspect.getsource(f)) for f in F]
print(f'The following lambdas had incorrect signatures:\n{"".join(_sources)}')
print(f'The following lambdas passed the test:\n{"".join(sources)}')

# Output
'''
This lambda has 2 arg - OK

This lambda has 1 arg - OK

This lambda has 3 arg - OK

Error: Incorrect number of arguments found in lambda structure - FAIL

The following lambdas had incorrect signatures:

  lambda a,b,c,d: a+b+c+d,

The following lambdas passed the test:

  lambda x,y: x+y,

  lambda x: x+1,

  lambda x,y,z: x*y*z,
'''