diff options
| -rw-r--r-- | Doc/lib/libitertools.tex | 15 | ||||
| -rw-r--r-- | Lib/test/test_itertools.py | 14 |
2 files changed, 28 insertions, 1 deletions
diff --git a/Doc/lib/libitertools.tex b/Doc/lib/libitertools.tex index 51570ee..d07ef2b 100644 --- a/Doc/lib/libitertools.tex +++ b/Doc/lib/libitertools.tex @@ -406,12 +406,25 @@ Samuele 2 ['b', 'd', 'f'] 3 ['g'] +# Find runs of consecutive numbers using groupby. The key to the solution +# is differencing with a range so that consecutive numbers all appear in +# same group. +>>> data = [ 1, 4,5,6, 10, 15,16,17,18, 22, 25,26,27,28] +>>> for k, g in groupby(enumerate(data), lambda (i,x):i-x): +... print map(operator.itemgetter(1), g) +... +[1] +[4, 5, 6] +[10] +[15, 16, 17, 18] +[22] +[25, 26, 27, 28] \end{verbatim} This section shows how itertools can be combined to create other more powerful itertools. Note that \function{enumerate()} and \method{iteritems()} -already have efficient implementations in Python. They are only included here +already have efficient implementations. They are included here to illustrate how higher level tools can be created from building blocks. \begin{verbatim} diff --git a/Lib/test/test_itertools.py b/Lib/test/test_itertools.py index 31b1b7c..fe49f75 100644 --- a/Lib/test/test_itertools.py +++ b/Lib/test/test_itertools.py @@ -677,6 +677,20 @@ Samuele 2 ['b', 'd', 'f'] 3 ['g'] +# Find runs of consecutive numbers using groupby. The key to the solution +# is differencing with a range so that consecutive numbers all appear in +# same group. +>>> data = [ 1, 4,5,6, 10, 15,16,17,18, 22, 25,26,27,28] +>>> for k, g in groupby(enumerate(data), lambda (i,x):i-x): +... print map(operator.itemgetter(1), g) +... +[1] +[4, 5, 6] +[10] +[15, 16, 17, 18] +[22] +[25, 26, 27, 28] + >>> def take(n, seq): ... return list(islice(seq, n)) |