[Python-checkins] peps: BDFL pronouncements.

Wed Mar 23 21:23:50 CET 2011

http://hg.python.org/peps/rev/8cd249c174a0
changeset: 59:8cd249c174a0
user: Guido van Rossum <guido at python.org>
date: Thu Jul 27 20:13:39 2000 +0000
summary:
 BDFL pronouncements.
Got rid of ^L.
files:
 pep-0202.txt | 33 +++++++++++++++++++++++----------
 1 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/pep-0202.txt b/pep-0202.txt
--- a/pep-0202.txt
+++ b/pep-0202.txt
@@ -5,14 +5,14 @@
 Python-Version: 2.0
 Status: Incomplete
 
-
+
 Introduction
 
 This PEP describes a proposed syntactical extension to Python, list
 comprehensions. 
 
 
-
+
 The Proposed Solution
 
 It is proposed to allow conditional construction of list literals using
@@ -20,14 +20,14 @@
 statements nest now.
 
 
-
+
 Rationale
 
 List comprehensions provide a more concise way to create lists in
 situations where map() and filter() and/or nested loops would currently
 be used.
 
-
+
 Examples
 
 >>> print [i for i in range(10)]
@@ -38,17 +38,17 @@
 
 >>> nums = [1,2,3,4]
 >>> fruit = ["Apples", "Peaches", "Pears", "Bananas"]
- >>> print [i,f for i in nums for f in fruit]
+ >>> print [(i,f) for i in nums for f in fruit]
 [(1, 'Apples'), (1, 'Peaches'), (1, 'Pears'), (1, 'Bananas'),
 (2, 'Apples'), (2, 'Peaches'), (2, 'Pears'), (2, 'Bananas'),
 (3, 'Apples'), (3, 'Peaches'), (3, 'Pears'), (3, 'Bananas'),
 (4, 'Apples'), (4, 'Peaches'), (4, 'Pears'), (4, 'Bananas')]
- >>> print [i,f for i in nums for f in fruit if f[0] == "P"]
+ >>> print [(i,f) for i in nums for f in fruit if f[0] == "P"]
 [(1, 'Peaches'), (1, 'Pears'),
 (2, 'Peaches'), (2, 'Pears'),
 (3, 'Peaches'), (3, 'Pears'),
 (4, 'Peaches'), (4, 'Pears')]
- >>> print [i,f for i in nums for f in fruit if f[0] == "P" if i%2 == 1]
+ >>> print [(i,f) for i in nums for f in fruit if f[0] == "P" if i%2 == 1]
 [(1, 'Peaches'), (1, 'Pears'), (3, 'Peaches'), (3, 'Pears')]
 >>> def zip(*args):
 ... return apply(map, (None,)+args)
@@ -56,7 +56,7 @@
 >>> print [i for i in zip(nums,fruit) if i[0]%2==0]
 [(2, 'Peaches'), (4, 'Bananas')]
 
-
+
 Reference Implementation
 
 Please refer to 
@@ -66,7 +66,20 @@
 for a patch that adds list comprehensions to Python.
 
 
-
+BDFL Pronouncements
+
+ Note: the BDFL refers to Guido van Rossum, Python's Benevolent
+ Dictator For Life.
+
+ - The syntax proposed above is the Right One.
+
+ - The form [x, y for ...] should be disallowed; one should be
+ required to write [(x, y) for ...].
+
+ - The form [... for x... for y...] nests, with the last index
+ varying fastest, just like nested for loops.
+
+
 Open Issues
 
 Syntax
@@ -113,7 +126,7 @@
 is. It has not had a lot of exercise, though the patch does include
 a few test cases.
 
-
+
 Local Variables:
 mode: indented-text
 indent-tabs-mode: nil
-- 
Repository URL: http://hg.python.org/peps
