When a command string contains an operator such as + or **, a dispatch table maps that key to the function that should handle it. A dictionary stores the functions as values, so retrieving operations[op] produces a callable that can immediately receive the parsed operands. section 6.7
A practical dispatch-table workflow is:
- Define one function for each operation. section 6.7
- Map input keys such as +, -, or ** to those functions. section 6.7
- Split the input, unpack its parts, convert operands, and invoke the selected function. section 6.7
- Use maxsplit when the input may contain additional separators after the expected fields. section 6.7
Dynamic menu dispatch
A menu can accept keyword arguments whose names become menu options and whose zero-argument functions become handlers. The resulting dictionary is created dynamically with **kwargs; its keys can be sorted and joined to display valid choices. section 8.7
def add(a,b):
return a + b
def sub(a,b):
return a - b
def mul(a,b):
return a * b
def div(a,b):
return a / b
def pow(a,b):
return a ** b
def mod(a,b):
return a % b
def calc(to_solve):
operations = {'+' : add, #1
'-' : sub,
'*' : mul,
'/' : div,
'**' : pow,
'%' : mod}
op, first_s, second_s = to_solve.split() #2
first = int(first_s) #3
second = int(second_s)
return operations[op](first, second) #4
Complete prefix-calculator implementation showing operation registration, input unpacking, integer conversion, and callable lookup. section 6.7
