[segyio] 243/376: Support ignoring geometry in python.open

[Jørgen Kvalsvik]

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jokva-guest pushed a commit to branch debian
in repository segyio.

commit a412b87a4af129960f3650f428daf58e2c9e2ec5
Author: Jørgen Kvalsvik <jokva at statoil.com>
Date:   Tue Mar 14 18:06:04 2017 +0100

    Support ignoring geometry in python.open
    
    For some uses, ignoring geometry means fewer headers scanned, which can
    be useful because it means faster opening of large files without
    meaningful xline/iline organisation.
---
 python/segyio/open.py | 17 ++++++++++++++++-
 python/test/segy.py   |  5 +++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/python/segyio/open.py b/python/segyio/open.py
index 82d238c..075b9e7 100644
--- a/python/segyio/open.py
+++ b/python/segyio/open.py
@@ -3,7 +3,10 @@ import numpy
 import segyio
 
 
-def open(filename, mode="r", iline=189, xline=193, strict = True):
+def open(filename, mode="r", iline = 189,
+                             xline = 193,
+                             strict = True,
+                             ignore_geometry = False):
     """Open a segy file.
 
     Opens a segy file and tries to figure out its sorting, inline numbers,
@@ -26,6 +29,11 @@ def open(filename, mode="r", iline=189, xline=193, strict = True):
     but it won't abort if it fails. When in non-strict mode is opened,
     geometry-dependent modes such as iline will raise an error.
 
+    If 'ignore_geometry' is set to True, segyio will *not* try to build
+    iline/xline or other geometry related structures, which leads to faster
+    opens. This is essentially the same as using strict = False on a file that
+    has no geometry.
+
     Args:
         filename (str): Path to file to open.
         mode (str, optional): File access mode, defaults to "r".
@@ -35,6 +43,9 @@ def open(filename, mode="r", iline=189, xline=193, strict = True):
                             Defaults to 193 as per the SEGY specification.
         strict (bool, optional): Abort if a geometry cannot be inferred.
                                  Defaults to True.
+        ignore_geometry (bool, optional): Opt out on building geometry
+                                          information, useful for e.g. shot
+                                          organised files. Defaults to False.
 
     Examples:
         Open a file in read-only mode::
@@ -73,6 +84,10 @@ def open(filename, mode="r", iline=189, xline=193, strict = True):
     except:
         f.close()
         raise
+
+    if ignore_geometry:
+        return f
+
     try:
         cube_metrics = segyio._segyio.init_cube_metrics(f.xfd,
                                                         iline,
diff --git a/python/test/segy.py b/python/test/segy.py
index ff97caa..6ab1480 100644
--- a/python/test/segy.py
+++ b/python/test/segy.py
@@ -177,6 +177,11 @@ class TestSegy(TestCase):
         with segyio.open(self.filename, strict = False):
             pass
 
+    def test_open_ignore_geometry(self):
+        with segyio.open(self.filename, ignore_geometry = True) as f:
+            with self.assertRaises(ValueError):
+                f.iline[0]
+
     def test_traces_slicing(self):
         with segyio.open(self.filename, "r") as f:
 

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