I'm trying to improve my Python style.
Consider a simple function which returns the first element of an iterable
if it has exactly one element, and throws an exception otherwise. It should
work even if the iterable doesn't terminate. I've written this function in
multiple ways, all of which feel a bit clumsy.
I'd be interested to hear thoughts on which of these solutions is most
Pythonic in style. And of course if there is a more elegant way to solve
this, I'm all ears! I'm probably missing something obvious!
Thanks,
-s
def firsta(iterable):
it = iter(iterable)
try:
val = next(it)
except StopIteration:
raise ValueError("first1: arg not exactly 1 long")
try:
next(it)
except StopIteration:
return val
raise ValueError("first1: arg not exactly 1 long")
def firstb(iterable):
it = iter(iterable)
try:
val = next(it)
except StopIteration:
raise ValueError("first1: arg not exactly 1 long")
try:
next(it)
except StopIteration:
return val
else:
raise ValueError("first1: arg not exactly 1 long")
def firstc(iterable):
it = iter(iterable)
try:
val = next(it)
except StopIteration:
raise ValueError("first1: arg not exactly 1 long")
try:
next(it)
raise ValueError("first1: arg not exactly 1 long")
except StopIteration:
return val
def firstd(iterable):
it = iter(iterable)
try:
val = next(it)
except StopIteration:
raise ValueError("first1: arg not exactly 1 long")
for i in it:
raise ValueError("first1: arg not exactly 1 long")
return val
def firste(iterable):
it = iter(iterable)
try:
good = False
val = next(it)
good = True
val = next(it)
good = False
raise StopIteration # or raise ValueError
except StopIteration:
if good:
return val
else:
raise ValueError("first1: arg not exactly 1 long")
def firstf(iterable):
n = -1
for n,i in enumerate(iterable):
if n>0:
raise ValueError("first1: arg not exactly 1 long")
if n==0:
return i
else:
raise ValueError("first1: arg not exactly 1 long")
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