Python Generator Cheatsheet

python_generators.py

# A personal cheatsheet for the confusing (to me) python feature: generators
# Done in ipython

[n*2 for n in [1,2,3]]
# Out[8]: [2, 4, 6]

{n*2 for n in [1,2,3] if n > 1}
# Out[9]: {4, 6}

for n in (x for x in [1,2,3] if x > 1):
  print(n*3)

# 6
# 9


# Generators
def abc():
  return 1
  return 2
  return 3

abc()
# 1
abc()
# 1

# useless because return short-circuits, just showing this as compared to what's next

# More useful:
def abc():
  yield 1
  yield 2

[ print(x) for x in abc() ]
# 1
# 2

# Save handle to generator:
gen = abc()
next(gen)
# Out[34]: 1

next(gen)
# Out[35]: 2

# you can't keep going
next(gen)
# ---------------------------------------------------------------------------
# StopIteration                             Traceback (most recent call last)
# <ipython-input-36-6e72e47198db> in <module>()
# ----> 1 next(gen)
# StopIteration: