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Replace magic numbers with constants.

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This commit is contained in:
Robert Smallshire
2011-10-19 00:34:18 +02:00
parent 865994b1ad
commit 6ccf6bac71
1 changed files with 14 additions and 12 deletions
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segypy.py
+14 -12
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@@ -1,4 +1,3 @@
"""
A python module for reading/writing/manipulating
SEG-Y formatted filed
@@ -40,6 +39,9 @@ from numpy import arange
version = '0.3.1' # modified by A Squelch
verbose = 1
REEL_HEADER_NUM_BYTES = 3600
TRACE_HEADER_NUM_BYTES = 240
#endian = '>' # Big Endian # modified by A Squelch
#endian = '<' # Little Endian
#endian = '=' # Native
@@ -445,7 +447,7 @@ def getSegyTraceHeader(SH, THN='cdp', data='none', endian='>'): # modified by A
thv = zeros(ntraces)
for itrace in range(1, ntraces+1, 1):
pos = THpos + 3600 + (SH["ns"] * bps + 240) * (itrace - 1)
pos = THpos + REEL_HEADER_NUM_BYTES + (SH["ns"] * bps + TRACE_HEADER_NUM_BYTES) * (itrace - 1)
txt = "getSegyTraceHeader : Reading trace header " + THN + " " + str(itrace) + " of " + str(ntraces) + " " +str(pos)
@@ -473,7 +475,7 @@ def getLastSegyTraceHeader(SH, THN='cdp', data='none', endian='>'): # added by
THformat = STH_def[THN]["type"]
ntraces = SH["ntraces"]
pos = THpos + 3600 + (SH["ns"] * bps + 240) * (ntraces - 1)
pos = THpos + REEL_HEADER_NUM_BYTES + (SH["ns"] * bps + TRACE_HEADER_NUM_BYTES) * (ntraces - 1)
txt = "getLastSegyTraceHeader : Reading last trace header " + THN + " " + str(pos)
@@ -520,7 +522,7 @@ def readSegy(filename, endian='>'): # modified by A Squelch
bps = getBytePerSample(SH)
ntraces = (filesize - 3600) / (SH['ns'] * bps + 240)
ntraces = (filesize - REEL_HEADER_NUM_BYTES) / (SH['ns'] * bps + TRACE_HEADER_NUM_BYTES)
printverbose("readSegy : Length of data : " + str(filesize), 2)
@@ -530,8 +532,8 @@ def readSegy(filename, endian='>'): # modified by A Squelch
# GET TRACE
index = 3600
nd = (filesize - 3600) / bps
index = REEL_HEADER_NUM_BYTES
nd = (filesize - REEL_HEADER_NUM_BYTES) / bps
Data, SH, SegyTraceHeaders = readSegyData(data, SH, nd, bps, index, endian)
@@ -549,7 +551,7 @@ def readSegyData(data, SH, nd, bps, index, endian='>'): # added by A Squelch
"""
# Calculate number of dummy samples needed to account for Trace Headers
ndummy_samples = 240 / bps
ndummy_samples = TRACE_HEADER_NUM_BYTES / bps
printverbose("readSegyData : ndummy_samples = " + str(ndummy_samples), 6)
# READ ALL SEGY TRACE HEADERS
@@ -632,7 +634,7 @@ def getSegyTrace(SH, itrace, endian='>'): # modified by A Squelch
SegyTraceHeader = []
# GET TRACE
index = 3200 + (itrace - 1) * (240 + SH['ns'] * bps) + 240
index = 3200 + (itrace - 1) * (TRACE_HEADER_NUM_BYTES + SH['ns'] * bps) + TRACE_HEADER_NUM_BYTES
SegyTraceData = getValue(data, index, 'float', endian, SH['ns'])
return SegyTraceHeader, SegyTraceData
@@ -657,7 +659,7 @@ def getSegyHeader(filename, endian='>'): # modified by A Squelch
bps = getBytePerSample(SegyHeader)
filesize = len(data)
ntraces = (filesize - 3600) / (SegyHeader['ns'] * bps + 240)
ntraces = (filesize - REEL_HEADER_NUM_BYTES) / (SegyHeader['ns'] * bps + TRACE_HEADER_NUM_BYTES)
SegyHeader["ntraces"] = ntraces
printverbose('getSegyHeader : succesfully read '+filename, 1)
@@ -754,10 +756,10 @@ def writeSegyStructure(filename, Data, SH, STH, endian='>'): # modified by A Sq
bps = SH_def['DataSampleFormat']['bps'][revision][dsf]
sizeT = 240 + SH['ns'] * bps
sizeT = TRACE_HEADER_NUM_BYTES + SH['ns'] * bps
for itrace in range(SH['ntraces']):
index = 3600 + itrace * sizeT
index = REEL_HEADER_NUM_BYTES + itrace * sizeT
printverbose('Writing Trace #' + str(itrace + 1) + '/' + str(SH['ntraces']), 10)
# WRITE SEGY TRACE HEADER
for key in STH_def.keys():
@@ -772,7 +774,7 @@ def writeSegyStructure(filename, Data, SH, STH, endian='>'): # modified by A Sq
cformat = endian + ctype
for s in range(SH['ns']):
strVal = struct.pack(cformat, Data[s, itrace])
f.seek(index + 240 + s * struct.calcsize(cformat))
f.seek(index + TRACE_HEADER_NUM_BYTES + s * struct.calcsize(cformat))
f.write(strVal)
f.close