Hello list, I'm trying to use Pytables and have run into a problem.
I first create a table with some initial values, but at some point I have to
add some columns. I have seen an example of this in the
*examples/*directory in the source package (
http://pytables.org/svn/pytables/branches/std-2.1/examples/add-column.py).
The example seems to run fine... unless I carry on appending rows to the
table after I add the column. See below the modified example which is giving
me problems.
Armando.
-----
"Modified from
http://pytables.org/svn/pytables/branches/std-2.1/examples/add-column.py";
from tables import *
class Particle(IsDescription):
name = StringCol(16, pos=1) # 16-character String
lati = Int32Col(pos=2) # integer
longi = Int32Col(pos=3) # integer
pressure = Float32Col(pos=4) # float (single-precision)
temperature = Float64Col(pos=5) # double (double-precision)
# Open a file in "w"rite mode
fileh = openFile("add-column.h5", mode = "w")
# Create a new group
group = fileh.createGroup(fileh.root, "newgroup")
# Create a new table in newgroup group
table = fileh.createTable(group, 'table', Particle, "A table", Filters(1))
# Append several rows
table.append([("Particle: 10", 10, 0, 10*10, 10**2),
("Particle: 11", 11, -1, 11*11, 11**2),
("Particle: 12", 12, -2, 12*12, 12**2)])
print "Contents of the original table:", fileh.root.newgroup.table[:]
# close the file
fileh.close()
# Open it again in append mode
fileh = openFile("add-column.h5", "a")
group = fileh.root.newgroup
table = group.table
# Get a description of table in dictionary format
descr = table.description._v_colObjects
descr2 = descr.copy()
# Add a column to description
descr2["hot"] = BoolCol(dflt=False)
# Create a new table with the new description
table2 = fileh.createTable(group, 'table2', descr2, "A table", Filters(1))
# Fill the rows of new table with default values
for i in xrange(table.nrows):
table2.row.append()
# Flush the rows to disk
table2.flush()
# Copy the columns of source table to destination
for col in descr:
getattr(table2.cols, col)[:] = getattr(table.cols, col)[:]
# Fill the new column
table2.cols.hot[:] = [ row["temperature"] > 11**2 for row in table ]
# Remove the original table
table.remove()
# Move table2 to table
table2.move('/newgroup','table')
# Print the new table
print "Contents of the table with column added:",
fileh.root.newgroup.table[:]
# ADD ONE MORE ROW
row = fileh.root.newgroup.table.row
row['hot'] = True
row.append()
fileh.root.newgroup.table.flush() ## HERE I GET AN ERROR ... NoSuchNodeError
... table2 ...
# Finally, close the file
fileh.close()
------------------------------------------------------------------------------
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