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Mostly PEP8 cleanups in the course of reading the code.

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I took the liberty of adding a few specific exception types, some
documentation, and things like that, but this is mostly a cosmetic chance.
This commit is contained in:
Austin Bingham
2014-09-02 09:39:04 +02:00
parent dcac37022d
commit e02b7be182
5 changed files with 259 additions and 119 deletions
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reader.py
+121 -63
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@@ -3,31 +3,50 @@ from __future__ import print_function
from portability import seekable
from util import file_length, filename_from_handle
from datatypes import DATA_SAMPLE_FORMAT, CTYPE_DESCRIPTION, CTYPES
from toolkit import (extract_revision, bytes_per_sample, read_reel_header, catalog_traces, read_binary_values,
compile_trace_header_format, TraceHeader, REEL_HEADER_NUM_BYTES, TRACE_HEADER_NUM_BYTES)
from toolkit import (extract_revision,
bytes_per_sample,
read_reel_header,
catalog_traces,
read_binary_values,
compile_trace_header_format,
TraceHeader,
REEL_HEADER_NUM_BYTES,
TRACE_HEADER_NUM_BYTES)
def create_reader(fh, endian='>'):
"""Create a SegYReader (or one of its subclasses) based on performing a scan of SEG Y data.
"""Create a SegYReader (or one of its subclasses) based on performing
a scan of SEG Y data.
This function is the preferred method for creating SegYReader objects. It reads basic header
information and attempts to build indexes for traces, CDP numbers (for 2D surveys), and inline
and cross line co-ordinates (for 3D surveys) to facilitate subsequent random-access to traces.
This function is the preferred method for creating SegYReader
objects. It reads basic header information and attempts to build
indexes for traces, CDP numbers (for 2D surveys), and inline and
cross line co-ordinates (for 3D surveys) to facilitate subsequent
random-access to traces.
Args:
fh: A file-like-object open in binary mode positioned such that the
beginning of the reel header will be the next byte to be read. For disk-based
SEG Y files, this is the beginning of the file.
fh: A file-like-object open in binary mode positioned such
that the beginning of the reel header will be the next
byte to be read. For disk-based SEG Y files, this is the
beginning of the file.
endian: '>' for big-endian data (the standard and default), '<' for
little-endian (non-standard)
endian: '>' for big-endian data (the standard and default), '<'
for little-endian (non-standard)
Raises:
ValueError: ``fh`` is unsuitable for some reason, such as not
being open, not being seekable, not being in
binary mode, or being too short.
Returns:
A SegYReader object. Depending on the exact type of the SegYReader returned different capabilities may be
available. Inspect the returned object to determine these capabilities, or be prepared for capabilities not
defined in the SegYReader base class to be unavailable. The underlying file-like object must remain open
for the duration of use of the returned reader object. It is the caller's responsibility to close the
underlying file.
A SegYReader object. Depending on the exact type of the
SegYReader returned different capabilities may be
available. Inspect the returned object to determine these
capabilities, or be prepared for capabilities not defined in
the SegYReader base class to be unavailable. The underlying
file-like object must remain open for the duration of use of
the returned reader object. It is the caller's responsibility
to close the underlying file.
Example:
@@ -37,18 +56,23 @@ def create_reader(fh, endian='>'):
"""
if fh.encoding is not None:
raise TypeError("SegYReader must be provided with a binary mode file object")
raise TypeError(
"SegYReader must be provided with a binary mode file object")
if not seekable(fh):
raise TypeError("SegYReader must be provided with a seekable file object")
raise TypeError(
"SegYReader must be provided with a seekable file object")
if fh.closed:
raise ValueError("SegYReader must be provided with an open file object")
raise ValueError(
"SegYReader must be provided with an open file object")
num_file_bytes = file_length(fh)
if num_file_bytes < REEL_HEADER_NUM_BYTES:
raise ValueError("SEG Y file {!r} of {} bytes is too short".format(filename_from_handle(fh),
num_file_bytes))
raise ValueError(
"SEG Y file {!r} of {} bytes is too short".format(
filename_from_handle(fh),
num_file_bytes))
if endian not in ('<', '>'):
raise ValueError("Unrecognised endian value {!r}".format(endian))
@@ -59,37 +83,43 @@ def create_reader(fh, endian='>'):
trace_catalog, cdp_catalog, line_catalog = catalog_traces(fh, bps, endian)
if cdp_catalog is not None and line_catalog is None:
return SegYReader2D(fh, reel_header, trace_catalog, cdp_catalog, endian)
return SegYReader2D(fh, reel_header, trace_catalog,
cdp_catalog, endian)
if cdp_catalog is None and line_catalog is not None:
return SegYReader3D(fh, reel_header, trace_catalog, line_catalog, endian)
return SegYReader3D(fh, reel_header, trace_catalog,
line_catalog, endian)
return SegYReader(fh, reel_header, trace_catalog, endian)
class SegYReader(object):
"""A basic SEG Y reader.
Use to obtain read the reel header, the trace headers or trace values. Traces can be accessed
only by trace index.
Use to obtain read the reel header, the trace headers or trace
values. Traces can be accessed only by trace index.
"""
def __init__(self, fh, reel_header, trace_catalog, endian='>'):
"""Initialize a SegYReader around a file-like-object.
Note:
Usually a SegYReader is most easily constructed using the create_reader() function.
Usually a SegYReader is most easily constructed using the
create_reader() function.
Args:
fh: A file-like object, which must support seeking and support binary reading.
fh: A file-like object, which must support seeking and
support binary reading.
reel_header: A dictionary containing reel header data.
trace_catalog: A mapping from zero-based trace index to the byte-offset to
individual traces within the file.
trace_catalog: A mapping from zero-based trace index to
the byte-offset to individual traces within the file.
endian: '>' for big-endian data (the standard and default), '<' for
little-endian (non-standard)
"""
self._fh = fh
self._endian = endian
@@ -99,13 +129,15 @@ class SegYReader(object):
self._trace_catalog = trace_catalog
self._revision = extract_revision(self._reel_header)
self._bytes_per_sample = bytes_per_sample(self._reel_header, self.revision)
self._bytes_per_sample = bytes_per_sample(
self._reel_header, self.revision)
def trace_indexes(self):
"""An iterator over zero-based trace indexes.
Returns:
An iterator which yields integers in the range zero to num_traces() - 1
An iterator which yields integers in the range zero to
num_traces() - 1
"""
return iter(self._trace_catalog)
@@ -120,8 +152,8 @@ class SegYReader(object):
trace_index: An integer in the range zero to num_traces() - 1
Returns:
A 2-tuple containing a TraceHeader as the first item and a sequence of numeric trace samples
as the second item.
A 2-tuple containing a TraceHeader as the first item and a
sequence of numeric trace samples as the second item.
Example:
@@ -134,7 +166,8 @@ class SegYReader(object):
dsf = self._reel_header['DataSampleFormat']
ctype = DATA_SAMPLE_FORMAT[dsf]
pos = self._trace_catalog[trace_index] + TRACE_HEADER_NUM_BYTES
trace_values = read_binary_values(self._fh, pos, ctype, num_samples, self._endian)
trace_values = read_binary_values(
self._fh, pos, ctype, num_samples, self._endian)
return trace_header, trace_values
def read_trace_header(self, trace_index):
@@ -155,7 +188,8 @@ class SegYReader(object):
pos = self._trace_catalog[trace_index]
self._fh.seek(pos)
data = self._fh.read(TRACE_HEADER_NUM_BYTES)
trace_header = TraceHeader._make(self._trace_header_format.unpack(data))
trace_header = TraceHeader._make(
self._trace_header_format.unpack(data))
return trace_header
@property
@@ -163,7 +197,9 @@ class SegYReader(object):
"""The spatial dimensionality of the data.
Returns:
3 for 3D seismic volumes, 2 for 2D seismic lines, 1 for a single trace, otherwise 0.
3 for 3D seismic volumes, 2 for 2D seismic lines, 1 for a
single trace, otherwise 0.
"""
return self._dimensionality()
@@ -222,31 +258,40 @@ class SegYReader(object):
class SegYReader3D(SegYReader):
"""A reader for 3D seismic data.
In addition to the capabilities provided by the SegYReader base class, this reader
provides an index to facilitate random access to individual traces via crossline and
inline co-ordinates.
In addition to the capabilities provided by the SegYReader base
class, this reader provides an index to facilitate random access
to individual traces via crossline and inline co-ordinates.
"""
def __init__(self, fh, reel_header, trace_catalog, line_catalog, endian='>'):
def __init__(self,
fh,
reel_header,
trace_catalog,
line_catalog,
endian='>'):
"""Initialize a SegYReader3D around a file-like-object.
Note:
Usually a SegYReader is most easily constructed using the create_reader() function.
Usually a SegYReader is most easily constructed using the
create_reader() function.
Args:
fh: A file-like object, which must support seeking and support binary reading.
fh: A file-like object, which must support seeking and
support binary reading.
reel_header: A dictionary containing reel header data.
trace_catalog: A mapping from zero-based trace indexes to the byte-offset to
individual traces within the file.
trace_catalog: A mapping from zero-based trace indexes to
the byte-offset to individual traces within the file.
line_catalog: A mapping from (xline, inline) tuples to trace_indexes.
line_catalog: A mapping from (xline, inline) tuples to
trace_indexes.
endian: '>' for big-endian data (the standard and default), '<' for
little-endian (non-standard)
"""
super(SegYReader3D, self).__init__(fh, reel_header, trace_catalog, endian)
super(SegYReader3D, self).__init__(
fh, reel_header, trace_catalog, endian)
self._line_catalog = line_catalog
def _dimensionality(self):
@@ -271,7 +316,8 @@ class SegYReader3D(SegYReader):
return len(set(i for i, j in self._line_catalog))
def inline_xlines(self):
"""An iterator over all (xline_number, inline_number) tuples corresponding to traces.
"""An iterator over all (xline_number, inline_number) tuples
corresponding to traces.
"""
return iter(self._line_catalog)
@@ -279,12 +325,14 @@ class SegYReader3D(SegYReader):
"""Obtain the trace index given an xline and a inline.
Note:
Do not assume that all combinations of crossline and inline co-ordinates are valid.
The volume may not be rectangular. Valid values can be obtained from the
Do not assume that all combinations of crossline and
inline co-ordinates are valid. The volume may not be
rectangular. Valid values can be obtained from the
inline_xlines() iterator.
Furthermore, inline and crossline numbers should not be relied upon to be zero- or one-based
indexes (although they may be).
Furthermore, inline and crossline numbers should not be
relied upon to be zero- or one-based indexes (although
they may be).
Args:
xline: A crossline number.
@@ -298,26 +346,34 @@ class SegYReader3D(SegYReader):
class SegYReader2D(SegYReader):
def __init__(self, fh, reel_header, trace_catalog, cdp_catalog, endian='>'):
def __init__(self,
fh,
reel_header,
trace_catalog,
cdp_catalog,
endian='>'):
"""Initialize a SegYReader2D around a file-like-object.
Note:
Usually a SegYReader is most easily constructed using the create_reader() function.
Usually a SegYReader is most easily constructed using the
create_reader() function.
Args:
fh: A file-like object, which must support seeking and support binary reading.
fh: A file-like object, which must support seeking and
support binary reading.
reel_header: A dictionary containing reel header data.
trace_catalog: A mapping from zero-based trace index to the byte-offset to
individual traces within the file.
trace_catalog: A mapping from zero-based trace index to
the byte-offset to individual traces within the file.
cdp_catalog: A mapping from CDP numbers to trace_indexes.
endian: '>' for big-endian data (the standard and default), '<' for
little-endian (non-standard)
"""
super(SegYReader2D, self).__init__(fh, reel_header, trace_catalog, endian)
super(SegYReader2D, self).__init__(
fh, reel_header, trace_catalog, endian)
self._cdp_catalog = cdp_catalog
def _dimensionality(self):
@@ -335,12 +391,14 @@ class SegYReader2D(SegYReader):
"""Obtain the trace index given an xline and a inline.
Note:
Do not assume that all combinations of crossline and inline co-ordinates are valid.
The volume may not be rectangular. Valid values can be obtained from the
Do not assume that all combinations of crossline and
inline co-ordinates are valid. The volume may not be
rectangular. Valid values can be obtained from the
inline_xlines() iterator.
Furthermore, inline and crossline numbers should not be relied upon to be zero- or one-based
indexes (although they may be).
Furthermore, inline and crossline numbers should not be
relied upon to be zero- or one-based indexes (although
they may be).
Args:
xline: A crossline number.
@@ -364,7 +422,8 @@ def main(argv=None):
print("Filename: ", segy_reader.filename)
print("SEG Y revision: ", segy_reader.revision)
print("Number of traces: ", segy_reader.num_traces())
print("Data format: ", segy_reader.data_sample_format_description)
print("Data format: ",
segy_reader.data_sample_format_description)
print("Dimensionality: ", segy_reader.dimensionality)
try:
@@ -380,4 +439,3 @@ def main(argv=None):
if __name__ == '__main__':
main()