Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
144 views
in Technique[技术] by (71.8m points)

python - "For" loop first iteration

I would like to inquire if there is an elegant pythonic way of executing some function on the first loop iteration. The only possibility I can think of is:

first = True
for member in something.get():
    if first:
        root.copy(member)
        first = False
    else:
        somewhereElse.copy(member)
    foo(member)
See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

Something like this should work.

for i, member in enumerate(something.get()):
    if i == 0:
         # Do thing
    # Code for everything

However, I would strongly recommend thinking about your code to see if you really have to do it this way, because it's sort of "dirty". Better would be to fetch the element that needs special handling up front, then do regular handling for all the others in the loop.

The only reason I could see for not doing it this way is for a big list you'd be getting from a generator expression (which you wouldn't want to fetch up front because it wouldn't fit in memory), or similar situations.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...