Strategy Pattern

The Idea

Find the one step that keeps changing, lift it into its own object with a fixed method name, and have the surrounding workflow call it. The workflow stops caring which variant is loaded, and adding a sixth variant never reopens it.

Real-World Example

Rally tyres. Same car, same driver, same stage — but slicks, wets or gravel go on the morning of the run, decided by the weather. Nobody builds a separate car per surface; the swappable part is bolted on last.

The Code

def slicks(base): return base * 1.0      # dry: full grip
def wets(base):   return base * 0.8      # safe in rain, slower
def gravel(base): return base * 0.6

class Stage:
    def __init__(self, tyres): self.tyres = tyres   # the swappable step
    def time(self, base): return round(120 / self.tyres(base), 2)

s = Stage(slicks)
print(s.time(1))                         # 120.0
s.tyres = wets                           # swapped between runs; Stage untouched
print(s.time(1))                         # 150.0
print(Stage(gravel).time(1))             # 200.0

def loud(s): return s.upper()
def quiet(s): return s.lower()

class Speaker:
  def __init__(self, style): self.style = style
  def say(self, s): return self.style(s)

sp = Speaker(loud)
out = [sp.say("Go")]
sp.style = quiet
out.append(sp.say("Go"))
print(out)