require list comprehensions to start with a for clause
diff --git a/Doc/ref/ref5.tex b/Doc/ref/ref5.tex
index 1abc6cb..f6d3b9c 100644
--- a/Doc/ref/ref5.tex
+++ b/Doc/ref/ref5.tex
@@ -153,7 +153,7 @@
\begin{verbatim}
list_display: "[" [listmaker] "]"
-listmaker: expression ( list_iter | ( "," expression)* [","] )
+listmaker: expression ( list_for | ( "," expression)* [","] )
list_iter: list_for | list_if
list_for: "for" expression_list "in" testlist [list_iter]
list_if: "if" test [list_iter]
@@ -164,7 +164,8 @@
When a comma-separated list of expressions is supplied, its elements are
evaluated from left to right and placed into the list object in that
order. When a list comprehension is supplied, it consists of a
-single expression followed by one or more "for" or "if" clauses. In this
+single expression followed by at least one "for" clause and zero or more
+"for" or "if" clauses. In this
case, the elements of the new list are those that would be produced
by considering each of the "for" or "if" clauses a block, nesting from
left to right, and evaluating the expression to produce a list element
diff --git a/Doc/tut/tut.tex b/Doc/tut/tut.tex
index 6451e2a..c5a9294 100644
--- a/Doc/tut/tut.tex
+++ b/Doc/tut/tut.tex
@@ -1755,10 +1755,15 @@
\subsection{List Comprehensions}
-List comprehensions provide a concise way to create lists without
-resorting to use of the \function{map()} or \function{filter()}
-functions. The resulting construct tends often to be clearer than use
-of those functions.
+List comprehensions provide a concise way to create lists without resorting
+to use of \function{map()}, \function{filter()} and/or \keyword{lambda}.
+The resulting list definition tends often to be clearer than lists built
+using those constructs. Each list comprehension consists of an expression
+following by a \keyword{for} clause, then zero or more \keyword{for} or
+\keyword{if} clauses. The result will be a list resulting from evaluating
+the expression in the context of the \keyword{for} and \keyword{if} clauses
+which follow it. If the expression would evaluate to a tuple, it must be
+parenthesized.
\begin{verbatim}
>>> freshfruit = [' banana', ' loganberry ', 'passion fruit ']
@@ -1771,6 +1776,17 @@
[12, 18]
>>> [3*x for x in vec if x < 2]
[]
+>>> [{x: x**2} for x in vec]
+[{2: 4}, {4: 16}, {6: 36}]
+>>> [[x,x**2] for x in vec]
+[[2, 4], [4, 16], [6, 36]]
+>>> [x, x**2 for x in vec] # error - parens required for tuples
+ File "<stdin>", line 1
+ [x, x**2 for x in vec]
+ ^
+SyntaxError: invalid syntax
+>>> [(x, x**2) for x in vec]
+[(2, 4), (4, 16), (6, 36)]
>>> vec1 = [2, 4, 6]
>>> vec2 = [4, 3, -9]
>>> [x*y for x in vec1 for y in vec2]
diff --git a/Grammar/Grammar b/Grammar/Grammar
index f95923d..dd12b6d 100644
--- a/Grammar/Grammar
+++ b/Grammar/Grammar
@@ -77,7 +77,7 @@
factor: ('+'|'-'|'~') factor | power
power: atom trailer* ('**' factor)*
atom: '(' [testlist] ')' | '[' [listmaker] ']' | '{' [dictmaker] '}' | '`' testlist '`' | NAME | NUMBER | STRING+
-listmaker: test ( list_iter | (',' test)* [','] )
+listmaker: test ( list_for | (',' test)* [','] )
lambdef: 'lambda' [varargslist] ':' test
trailer: '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAME
subscriptlist: subscript (',' subscript)* [',']
diff --git a/Lib/test/output/test_grammar b/Lib/test/output/test_grammar
index 203cf18..8a0c531 100644
--- a/Lib/test/output/test_grammar
+++ b/Lib/test/output/test_grammar
@@ -55,4 +55,5 @@
[(1, 'Apple'), (1, 'Banana'), (1, 'Coconut'), (2, 'Apple'), (2, 'Banana'), (2, 'Coconut'), (3, 'Apple'), (3, 'Banana'), (3, 'Coconut'), (4, 'Apple'), (4, 'Banana'), (4, 'Coconut'), (5, 'Apple'), (5, 'Banana'), (5, 'Coconut')]
[(1, 'Banana'), (1, 'Coconut'), (2, 'Banana'), (2, 'Coconut'), (3, 'Banana'), (3, 'Coconut'), (4, 'Banana'), (4, 'Coconut'), (5, 'Banana'), (5, 'Coconut')]
good: got a SyntaxError as expected
+good: got a SyntaxError as expected
[('Boeing', 'Airliner'), ('Boeing', 'Engine'), ('Ford', 'Engine'), ('Macdonalds', 'Cheeseburger')]
diff --git a/Lib/test/test_grammar.py b/Lib/test/test_grammar.py
index da74444..b0e3da9 100644
--- a/Lib/test/test_grammar.py
+++ b/Lib/test/test_grammar.py
@@ -578,6 +578,12 @@
except SyntaxError:
print "good: got a SyntaxError as expected"
+try:
+ eval("[x if y]")
+ print "FAIL: should have raised a SyntaxError!"
+except SyntaxError:
+ print "good: got a SyntaxError as expected"
+
suppliers = [
(1, "Boeing"),
(2, "Ford"),
diff --git a/Python/compile.c b/Python/compile.c
index e09204e..f239bb6 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -1043,7 +1043,7 @@
static void
com_list_comprehension(struct compiling *c, node *n)
{
- /* listmaker: test list_iter */
+ /* listmaker: test list_for */
char tmpname[12];
sprintf(tmpname, "__%d__", ++c->c_tmpname);
com_addoparg(c, BUILD_LIST, 0);
@@ -1052,7 +1052,7 @@
com_addopnamestr(c, LOAD_ATTR, "append");
com_addopnamestr(c, STORE_NAME, tmpname);
com_pop(c, 1);
- com_list_iter(c, n, CHILD(n, 0), tmpname);
+ com_list_for(c, CHILD(n, 1), CHILD(n, 0), tmpname);
com_addopnamestr(c, DELETE_NAME, tmpname);
--c->c_tmpname;
}
@@ -1060,8 +1060,8 @@
static void
com_listmaker(struct compiling *c, node *n)
{
- /* listmaker: test ( list_iter | (',' test)* [','] ) */
- if (NCH(n) > 1 && TYPE(CHILD(n, 1)) == list_iter)
+ /* listmaker: test ( list_for | (',' test)* [','] ) */
+ if (NCH(n) > 1 && TYPE(CHILD(n, 1)) == list_for)
com_list_comprehension(c, n);
else {
int len = 0;
diff --git a/Python/graminit.c b/Python/graminit.c
index a62b62e..c8570ff 100644
--- a/Python/graminit.c
+++ b/Python/graminit.c
@@ -1317,7 +1317,7 @@
{1, arcs_59_3},
};
static arc arcs_60_0[2] = {
- {128, 1},
+ {120, 1},
{129, 1},
};
static arc arcs_60_1[1] = {
@@ -1340,7 +1340,7 @@
{9, 4},
};
static arc arcs_61_4[2] = {
- {120, 5},
+ {128, 5},
{0, 4},
};
static arc arcs_61_5[1] = {
@@ -1361,7 +1361,7 @@
{21, 2},
};
static arc arcs_62_2[2] = {
- {120, 3},
+ {128, 3},
{0, 2},
};
static arc arcs_62_3[1] = {
@@ -1622,7 +1622,7 @@
{25, 0},
{2, 0},
{3, 0},
- {316, 0},
+ {317, 0},
{1, "lambda"},
{314, 0},
{307, 0},
@@ -1630,7 +1630,7 @@
{309, 0},
{1, "class"},
{315, 0},
- {317, 0},
+ {316, 0},
{318, 0},
};
grammar _PyParser_Grammar = {