[Tutor] sql-like join on two lists or dictionaries

[Alan Gauld]

On 14/02/15 09:55, Peter Otten wrote:

> with open(headerfile) as f:
>      lookup_header = {
>          headerdata[:6]: headerdata.rstrip("\n") for headerdata in f}
>
> Then you can iterate over the lines in linefile, extract the key from that
> and look it up in the dict:
>
> with open(linefile) as lines, open("hl.dat", "w") as joined:
>      for line in lines:
>          try:
>              header = lookup_header[line[:6]]
>          except KeyError:
>              header = ""
>          print(line.rstrip("\n"), header, sep="", file=joined)
>

The try/except could be written more concisely as

header = lookup_header.get(line[:6], "")


HTH
-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos