ASKSAGE: Sage Q&A Forum - Individual question feedhttp://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Wed, 06 Jun 2018 19:20:30 -0500preparser state for regexshttp://ask.sagemath.org/question/9277/preparser-state-for-regexs/I would have expected the following to work:
reset()
import re
preparser(False) # preparser off else we have \\ instead of \
rx=re.compile(r".*(\sHun\s).*") # in the regex
m = rx.match(r"The Attila the Hun Show") # Find "Hun" in "The Attila the Hun Show"
if m: print "found =>", m.group(1) # 1 needs to be 1 not '1' here!
preparser(True)
In fact I get 'IndexError: no such group'. Using int(1) fixes the problem, but why? The preparser is off!
Even more curious the block works, as is, on every other evaluate! I tried moving the preparser(False) statement to before the import, but that makes no difference.Thu, 30 Aug 2012 04:58:18 -0500http://ask.sagemath.org/question/9277/preparser-state-for-regexs/Answer by j.c. for <p>I would have expected the following to work:</p>
<pre><code>reset()
import re
preparser(False) # preparser off else we have \\ instead of \
rx=re.compile(r".*(\sHun\s).*") # in the regex
m = rx.match(r"The Attila the Hun Show") # Find "Hun" in "The Attila the Hun Show"
if m: print "found =>", m.group(1) # 1 needs to be 1 not '1' here!
preparser(True)
</code></pre>
<p>In fact I get 'IndexError: no such group'. Using int(1) fixes the problem, but why? The preparser is off!</p>
<p>Even more curious the block works, as is, on every other evaluate! I tried moving the preparser(False) statement to before the import, but that makes no difference.</p>
http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?answer=42530#post-id-42530I had a similar issue dealing with the preparser so I wrote an IPython extension which adds a cell magic `%%noparse` which disables the Sage preparser for the cell its applied to.
Save this code as `noparse.py`:
from IPython.core.magic import (Magics, magics_class, cell_magic)
import sage.repl.interpreter
@magics_class
class NoParseMagic(Magics):
@cell_magic
def noparse(self, line, cell):
"""
Use this cell magic to disable Sage preparsing in an IPython cell.
"""
sage.repl.interpreter._do_preparse = False
self.shell.run_cell(cell)
sage.repl.interpreter._do_preparse = True
def load_ipython_extension(ipython):
ipython.register_magics(NoParseMagic)
If you like, you can copy this to `.ipython/extensions/`. Then in a Sage Jupyter notebook, you can run:
%load_ext noparse
to load the extension. Now the following works:
%%noparse
type(4)
which yields:
<type 'int'>
instead of:
<type 'sage.rings.integer.Integer'>Wed, 06 Jun 2018 05:43:46 -0500http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?answer=42530#post-id-42530Comment by j.c. for <p>I had a similar issue dealing with the preparser so I wrote an IPython extension which adds a cell magic <code>%%noparse</code> which disables the Sage preparser for the cell its applied to.</p>
<p>Save this code as <code>noparse.py</code>:</p>
<pre><code>from IPython.core.magic import (Magics, magics_class, cell_magic)
import sage.repl.interpreter
@magics_class
class NoParseMagic(Magics):
@cell_magic
def noparse(self, line, cell):
"""
Use this cell magic to disable Sage preparsing in an IPython cell.
"""
sage.repl.interpreter._do_preparse = False
self.shell.run_cell(cell)
sage.repl.interpreter._do_preparse = True
def load_ipython_extension(ipython):
ipython.register_magics(NoParseMagic)
</code></pre>
<p>If you like, you can copy this to <code>.ipython/extensions/</code>. Then in a Sage Jupyter notebook, you can run:</p>
<pre><code>%load_ext noparse
</code></pre>
<p>to load the extension. Now the following works:</p>
<pre><code>%%noparse
type(4)
</code></pre>
<p>which yields:</p>
<pre><code><type 'int'>
</code></pre>
<p>instead of:</p>
<pre><code><type 'sage.rings.integer.Integer'>
</code></pre>
http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?comment=42538#post-id-42538Here is the ticket https://trac.sagemath.org/ticket/25522Wed, 06 Jun 2018 19:20:30 -0500http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?comment=42538#post-id-42538Comment by j.c. for <p>I had a similar issue dealing with the preparser so I wrote an IPython extension which adds a cell magic <code>%%noparse</code> which disables the Sage preparser for the cell its applied to.</p>
<p>Save this code as <code>noparse.py</code>:</p>
<pre><code>from IPython.core.magic import (Magics, magics_class, cell_magic)
import sage.repl.interpreter
@magics_class
class NoParseMagic(Magics):
@cell_magic
def noparse(self, line, cell):
"""
Use this cell magic to disable Sage preparsing in an IPython cell.
"""
sage.repl.interpreter._do_preparse = False
self.shell.run_cell(cell)
sage.repl.interpreter._do_preparse = True
def load_ipython_extension(ipython):
ipython.register_magics(NoParseMagic)
</code></pre>
<p>If you like, you can copy this to <code>.ipython/extensions/</code>. Then in a Sage Jupyter notebook, you can run:</p>
<pre><code>%load_ext noparse
</code></pre>
<p>to load the extension. Now the following works:</p>
<pre><code>%%noparse
type(4)
</code></pre>
<p>which yields:</p>
<pre><code><type 'int'>
</code></pre>
<p>instead of:</p>
<pre><code><type 'sage.rings.integer.Integer'>
</code></pre>
http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?comment=42537#post-id-42537Thanks, I'll see if I can figure out how to do that later tonight.Wed, 06 Jun 2018 13:54:26 -0500http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?comment=42537#post-id-42537Comment by nbruin for <p>I had a similar issue dealing with the preparser so I wrote an IPython extension which adds a cell magic <code>%%noparse</code> which disables the Sage preparser for the cell its applied to.</p>
<p>Save this code as <code>noparse.py</code>:</p>
<pre><code>from IPython.core.magic import (Magics, magics_class, cell_magic)
import sage.repl.interpreter
@magics_class
class NoParseMagic(Magics):
@cell_magic
def noparse(self, line, cell):
"""
Use this cell magic to disable Sage preparsing in an IPython cell.
"""
sage.repl.interpreter._do_preparse = False
self.shell.run_cell(cell)
sage.repl.interpreter._do_preparse = True
def load_ipython_extension(ipython):
ipython.register_magics(NoParseMagic)
</code></pre>
<p>If you like, you can copy this to <code>.ipython/extensions/</code>. Then in a Sage Jupyter notebook, you can run:</p>
<pre><code>%load_ext noparse
</code></pre>
<p>to load the extension. Now the following works:</p>
<pre><code>%%noparse
type(4)
</code></pre>
<p>which yields:</p>
<pre><code><type 'int'>
</code></pre>
<p>instead of:</p>
<pre><code><type 'sage.rings.integer.Integer'>
</code></pre>
http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?comment=42535#post-id-42535I think this deserves to be added to the sage ipython kernel. Would you mind making a ticket for this?Wed, 06 Jun 2018 13:10:48 -0500http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?comment=42535#post-id-42535Answer by John Palmieri for <p>I would have expected the following to work:</p>
<pre><code>reset()
import re
preparser(False) # preparser off else we have \\ instead of \
rx=re.compile(r".*(\sHun\s).*") # in the regex
m = rx.match(r"The Attila the Hun Show") # Find "Hun" in "The Attila the Hun Show"
if m: print "found =>", m.group(1) # 1 needs to be 1 not '1' here!
preparser(True)
</code></pre>
<p>In fact I get 'IndexError: no such group'. Using int(1) fixes the problem, but why? The preparser is off!</p>
<p>Even more curious the block works, as is, on every other evaluate! I tried moving the preparser(False) statement to before the import, but that makes no difference.</p>
http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?answer=13975#post-id-13975This works for me from the command line. In the notebook, it fails the first time and succeeds the second time. Indeed, having a notebook cell containing
preparser(False)
type(2)
fails the first time I evaluate it and succeeds the second time. **This is what is supposed to happen, though.** Consider this, from the command-line:
sage: preparser(False); type(2)
The first thing that happens is that the whole line gets preparsed, so "2" gets turned into "Integer(2)". Then the line gets evaluated, so it turns the preparser off and it returns the type of "Integer(2)", namely `sage.rings.integer.Integer`. I think that the same thing happens in each cell of the notebook: the whole thing gets preparsed before any of it is evaluated. So you need to put `preparser(False)` in a separate cell and evaluate it first.Thu, 30 Aug 2012 05:57:12 -0500http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?answer=13975#post-id-13975Comment by John Palmieri for <p>This works for me from the command line. In the notebook, it fails the first time and succeeds the second time. Indeed, having a notebook cell containing</p>
<pre><code>preparser(False)
type(2)
</code></pre>
<p>fails the first time I evaluate it and succeeds the second time. <strong>This is what is supposed to happen, though.</strong> Consider this, from the command-line:</p>
<pre><code>sage: preparser(False); type(2)
</code></pre>
<p>The first thing that happens is that the whole line gets preparsed, so "2" gets turned into "Integer(2)". Then the line gets evaluated, so it turns the preparser off and it returns the type of "Integer(2)", namely <code>sage.rings.integer.Integer</code>. I think that the same thing happens in each cell of the notebook: the whole thing gets preparsed before any of it is evaluated. So you need to put <code>preparser(False)</code> in a separate cell and evaluate it first.</p>
http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?comment=19136#post-id-19136I don't see anything wrong with these two cells. Any "preparser" commands cannot affect the current cell, since they haven't been evaluated yet. Once the cell has been evaluated (in its entirety), they affect any further cells, so for both of your cells, since they both end in "preparser(True)", the preparser is on all the time. If you remove the last "preparser(True)" from cell 2, then after evaluating that cell, the preparser will be off for any subsequent evaluations.Thu, 30 Aug 2012 11:48:07 -0500http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?comment=19136#post-id-19136Comment by oldbrad for <p>This works for me from the command line. In the notebook, it fails the first time and succeeds the second time. Indeed, having a notebook cell containing</p>
<pre><code>preparser(False)
type(2)
</code></pre>
<p>fails the first time I evaluate it and succeeds the second time. <strong>This is what is supposed to happen, though.</strong> Consider this, from the command-line:</p>
<pre><code>sage: preparser(False); type(2)
</code></pre>
<p>The first thing that happens is that the whole line gets preparsed, so "2" gets turned into "Integer(2)". Then the line gets evaluated, so it turns the preparser off and it returns the type of "Integer(2)", namely <code>sage.rings.integer.Integer</code>. I think that the same thing happens in each cell of the notebook: the whole thing gets preparsed before any of it is evaluated. So you need to put <code>preparser(False)</code> in a separate cell and evaluate it first.</p>
http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?comment=19137#post-id-19137No no no .. Something infinitly more diabolical! Experement with two cells as follows
Cell one:
preparser(False); print type(2)
preparser(True); print type(2)
Cell two:
preparser(True); print type(2)
preparser(False); print type(2)
preparser(True)
Also comment the last and see what happens. I'm totaly confused.
I anycase, surely one should leave the preparser in the on state?
Thu, 30 Aug 2012 10:33:16 -0500http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?comment=19137#post-id-19137Comment by John Palmieri for <p>This works for me from the command line. In the notebook, it fails the first time and succeeds the second time. Indeed, having a notebook cell containing</p>
<pre><code>preparser(False)
type(2)
</code></pre>
<p>fails the first time I evaluate it and succeeds the second time. <strong>This is what is supposed to happen, though.</strong> Consider this, from the command-line:</p>
<pre><code>sage: preparser(False); type(2)
</code></pre>
<p>The first thing that happens is that the whole line gets preparsed, so "2" gets turned into "Integer(2)". Then the line gets evaluated, so it turns the preparser off and it returns the type of "Integer(2)", namely <code>sage.rings.integer.Integer</code>. I think that the same thing happens in each cell of the notebook: the whole thing gets preparsed before any of it is evaluated. So you need to put <code>preparser(False)</code> in a separate cell and evaluate it first.</p>
http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?comment=19135#post-id-19135You're missing some semicolons, by the way. Cell 1 should be `preparser(False); print type(2); preparser(True); print type(2)`, and cell 2 should be `preparser(True); print type(2); preparser(False); print type(2); preparser(True)`.Thu, 30 Aug 2012 11:49:07 -0500http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?comment=19135#post-id-19135Answer by John Palmieri for <p>I would have expected the following to work:</p>
<pre><code>reset()
import re
preparser(False) # preparser off else we have \\ instead of \
rx=re.compile(r".*(\sHun\s).*") # in the regex
m = rx.match(r"The Attila the Hun Show") # Find "Hun" in "The Attila the Hun Show"
if m: print "found =>", m.group(1) # 1 needs to be 1 not '1' here!
preparser(True)
</code></pre>
<p>In fact I get 'IndexError: no such group'. Using int(1) fixes the problem, but why? The preparser is off!</p>
<p>Even more curious the block works, as is, on every other evaluate! I tried moving the preparser(False) statement to before the import, but that makes no difference.</p>
http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?answer=13974#post-id-13974This works for me from the command line. In the notebook, it fails the first time and succeeds the second time. Indeed, having a notebook cell containing
preparser(False)
type(1)
fails the first time I evaluate it and succeeds the second time. Must be a bug somewhere.Thu, 30 Aug 2012 05:32:03 -0500http://ask.sagemath.org/question/9277/preparser-state-for-regexs/?answer=13974#post-id-13974