Re: [Pytables-users] modifying a table column
Hey Sasha, You probably want to look at the Expr class [1] where you set out to be the same as the original array. Be Well Anthony 1. http://pytables.github.io/usersguide/libref/expr_class.html On Tue, Aug 27, 2013 at 11:44 AM, Oleksandr Huziy guziy.sa...@gmail.comwrote: Hi All: I have a huge table imported from other binary files to hdf, and I forgot to multiply the data by a factor in one case. Is there an easy way to multiply a column by a constant factor using pytables? To modify it in place? Thank you -- Sasha -- Learn the latest--Visual Studio 2012, SharePoint 2013, SQL 2012, more! Discover the easy way to master current and previous Microsoft technologies and advance your career. Get an incredible 1,500+ hours of step-by-step tutorial videos with LearnDevNow. Subscribe today and save! http://pubads.g.doubleclick.net/gampad/clk?id=58040911iu=/4140/ostg.clktrk ___ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users -- Learn the latest--Visual Studio 2012, SharePoint 2013, SQL 2012, more! Discover the easy way to master current and previous Microsoft technologies and advance your career. Get an incredible 1,500+ hours of step-by-step tutorial videos with LearnDevNow. Subscribe today and save! http://pubads.g.doubleclick.net/gampad/clk?id=58040911iu=/4140/ostg.clktrk___ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users
Re: [Pytables-users] modifying a table column
Thank you Anthony. Cheers 2013/8/27 Anthony Scopatz scop...@gmail.com Hey Sasha, You probably want to look at the Expr class [1] where you set out to be the same as the original array. Be Well Anthony 1. http://pytables.github.io/usersguide/libref/expr_class.html On Tue, Aug 27, 2013 at 11:44 AM, Oleksandr Huziy guziy.sa...@gmail.comwrote: Hi All: I have a huge table imported from other binary files to hdf, and I forgot to multiply the data by a factor in one case. Is there an easy way to multiply a column by a constant factor using pytables? To modify it in place? Thank you -- Sasha -- Learn the latest--Visual Studio 2012, SharePoint 2013, SQL 2012, more! Discover the easy way to master current and previous Microsoft technologies and advance your career. Get an incredible 1,500+ hours of step-by-step tutorial videos with LearnDevNow. Subscribe today and save! http://pubads.g.doubleclick.net/gampad/clk?id=58040911iu=/4140/ostg.clktrk ___ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users -- Learn the latest--Visual Studio 2012, SharePoint 2013, SQL 2012, more! Discover the easy way to master current and previous Microsoft technologies and advance your career. Get an incredible 1,500+ hours of step-by-step tutorial videos with LearnDevNow. Subscribe today and save! http://pubads.g.doubleclick.net/gampad/clk?id=58040911iu=/4140/ostg.clktrk ___ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users -- Learn the latest--Visual Studio 2012, SharePoint 2013, SQL 2012, more! Discover the easy way to master current and previous Microsoft technologies and advance your career. Get an incredible 1,500+ hours of step-by-step tutorial videos with LearnDevNow. Subscribe today and save! http://pubads.g.doubleclick.net/gampad/clk?id=58040911iu=/4140/ostg.clktrk___ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users
Re: [Pytables-users] modifying a table column
On Tue, Aug 27, 2013 at 6:50 PM, Oleksandr Huziy guziy.sa...@gmail.comwrote:
Hi Again:
2013/8/27 Anthony Scopatz scop...@gmail.com
Hey Sasha,
You probably want to look at the Expr class [1] where you set out to be
the same as the original array.
Be Well
Anthony
1. http://pytables.github.io/usersguide/libref/expr_class.html
I just wanted to make sure if it is possible to use an assignment in
expressions? (this gives me a syntax error exception, complains about the
equal sign in the expression)
Hi Sasha,
Assignment is a statement not an expression, so it is not possible to use
here. This is why you are getting a syntax error.
h = tb.open_file(path, mode=a)
varTable = h.get_node(/, var_name)
coef = 3 * 60 * 60 #output step
expr = tb.Expr(c = c * m, uservars = {c: varTable.cols.field, m:
coef })
expr.eval()
varTable.flush()
h.close()
Is this an optimal way of multiplying a column? (this one works, but I
think it loads all the data into memory...right?)
expr = tb.Expr(c * m, uservars = {c: varTable.cols.field, m:
coef })
varTable.cols.field[:] = expr.eval()
You are right that this loads the entire computed array into memory and is
therefore not optimal. I would do something like the following:
h = tb.open_file(path, mode=a)
varTable = h.get_node(/, var_name)
coef = 3 * 60 * 60 #output step
c = varTable.cols.field
expr = tb.Expr(c = c * m, uservars = {c: c, m: coef })
expr.set_output(c)
expr.eval()
varTable.flush()
h.close()
Be Well
Anthony
Thank you
Cheers
On Tue, Aug 27, 2013 at 11:44 AM, Oleksandr Huziy guziy.sa...@gmail.com
wrote:
Hi All:
I have a huge table imported from other binary files to hdf, and I
forgot to multiply the data by a factor in one case. Is there an easy way
to multiply a column by a constant factor using pytables?
To modify it in place?
Thank you
--
Sasha
--
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Re: [Pytables-users] modifying a table column
2013/8/27 Anthony Scopatz scop...@gmail.com
You are right that this loads the entire computed array into memory and is
therefore not optimal. I would do something like the following:
h = tb.open_file(path, mode=a)
varTable = h.get_node(/, var_name)
coef = 3 * 60 * 60 #output step
c = varTable.cols.field
expr = tb.Expr(c * m, uservars = {c: c, m: coef })
expr.set_output(c)
expr.eval()
varTable.flush()
h.close()
Aha, this is cool. Thanks Anthony.
Cheers
--
Sasha
On Tue, Aug 27, 2013 at 11:44 AM, Oleksandr Huziy
guziy.sa...@gmail.com wrote:
Hi All:
I have a huge table imported from other binary files to hdf, and I
forgot to multiply the data by a factor in one case. Is there an easy way
to multiply a column by a constant factor using pytables?
To modify it in place?
Thank you
--
Sasha
--
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Re: [Pytables-users] modifying a table column
Glad I could help!
On Tue, Aug 27, 2013 at 7:44 PM, Oleksandr Huziy guziy.sa...@gmail.comwrote:
2013/8/27 Anthony Scopatz scop...@gmail.com
You are right that this loads the entire computed array into memory and
is therefore not optimal. I would do something like the following:
h = tb.open_file(path, mode=a)
varTable = h.get_node(/, var_name)
coef = 3 * 60 * 60 #output step
c = varTable.cols.field
expr = tb.Expr(c * m, uservars = {c: c, m: coef })
expr.set_output(c)
expr.eval()
varTable.flush()
h.close()
Aha, this is cool. Thanks Anthony.
Cheers
--
Sasha
On Tue, Aug 27, 2013 at 11:44 AM, Oleksandr Huziy
guziy.sa...@gmail.com wrote:
Hi All:
I have a huge table imported from other binary files to hdf, and I
forgot to multiply the data by a factor in one case. Is there an easy way
to multiply a column by a constant factor using pytables?
To modify it in place?
Thank you
--
Sasha
--
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