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# This is an example on how to use complex columns
import numpy as np
import tables as tb
N = 1000
padded_dtype = np.dtype(
[("string", "S3"), ("int", "i4"), ("double", "f8")], align=True
)
# assert padded_dtype.itemsize == 16
padded_struct = np.zeros(N, padded_dtype)
padded_struct["string"] = np.arange(N).astype("S3")
padded_struct["int"] = np.arange(N, dtype="i4")
padded_struct["double"] = np.arange(N, dtype="f8")
# Create a file with padding (the default)
fileh = tb.open_file(
"tables-with-padding.h5", mode="w", pytables_sys_attrs=False
)
table = fileh.create_table(
fileh.root, "table", padded_struct, "A table with padding"
)
print("table *with* padding -->", table)
print("table.description --> ", table.description)
print("table.descrition._v_offsets-->", table.description._v_offsets)
print("table.descrition._v_itemsize-->", table.description._v_itemsize)
fileh.close()
# Create another file without padding
fileh = tb.open_file(
"tables-without-padding.h5",
mode="w",
pytables_sys_attrs=False,
allow_padding=False,
)
table = fileh.create_table(
fileh.root, "table", padded_struct, "A table without padding"
)
print("\ntable *without* padding -->", table)
print("table.description --> ", table.description)
print("table.descrition._v_offsets-->", table.description._v_offsets)
print("table.descrition._v_itemsize-->", table.description._v_itemsize)
fileh.close()
print("\n ***After closing***\n")
fileh = tb.open_file("tables-with-padding.h5", mode="r")
table = fileh.root.table
print("table *with* padding -->", table)
print("table.description --> ", table.description)
print("table.descrition._v_offsets-->", table.description._v_offsets)
print("table.descrition._v_itemsize-->", table.description._v_itemsize)
fileh.close()
fileh = tb.open_file("tables-without-padding.h5", mode="r")
table = fileh.root.table
print("\ntable *without* padding -->", table)
print("table.description --> ", table.description)
print("table.descrition._v_offsets-->", table.description._v_offsets)
print("table.descrition._v_itemsize-->", table.description._v_itemsize)
fileh.close()
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