Utility programs 3

Ok, time flies and all, but we better get some actual working code in this thing. In post 1 all we did was create a usage string and test argv to see if anything had been passed in (in this case we don't want anything). In the second we used glob to build a list of files matching a certain extension in the directory we're working in. Eventually we could us a windows file select dialog but for now this will be a simple command line utility. Let's get right to the pertinent section then put it all together in the end. Using th same indentation as where we left off, lets replace

........print os.path.splitext(File)

which was just used to show that something was working and to illustrate os.path functions with

# Step through the list of files processing each
....for File in Filelist:
# Each file will need to be opened
........OppFile=open(File,'r')
# readlines() reads every line in a file, returns a list in which each member
# of the list is a line in the file, including the end of line character.
........FileData=OppFile.readlines()
# Step through the list of lines in the open file
........for Line in FileData:
# This isn't real tricky or elegant, but it turns out that the coordinate
# positions stored in the .opp file are on lines which have an "l" as the
# second character, so let's just determine first of all if the data line
# is a coordinate
............if Line[1]=='l':
# Then if it is, the first character determines which coordinate it is.
# If it's an X, Y, or Z we'll use the split(function) to break the line
# into a list of strings, which contains the number as the second
# element, then use float() to convert it to a real number, and store it
# in the appropriate variable.
................if Line[0]=='X':
....................X=float(Line.split()[1])
................elif Line[0]=='Y':
....................Y=float(Line.split()[1])
................elif Line[0]=='Z':
....................Z=float(Line.split()[1])
# Once we have parsed each line in the file to pull out the coordinates
# lets use some formatted printing to output the file name and values.
# Remember that "File" contains the name of the file with the extension
# so the split using the dot will give a list ['filename','extension']
# so the base name is element 1 or [0]
# Close the file and your on your way.
........print '%s %.3lf %.3lf %.3lf'%(File.split('.')[0],X,Y,Z)
........OppFile.close()

so in the end after removing the modules that were only temporary, the final program looks like

import sys,glob

def usage():
....'''
....Explanation text to print if anything is entered as an argument.
....'''
....print '\nUsage: python opp2txt.py\nThere are no arguments, it will just look in the current directory\n for files with a .opp extension, strip the coordinates out of them\n and output them to the screen\n\nListings can be redirected into a file.\n eg: python opp2txt.py > photos.txt'
....sys.exit(1)

if len(sys.argv)==1:
....Filelist=glob.glob('*.opp')
....if Filelist==[]:
........print "There don't appear to be any .opp files in this directory"
........sys.exit(2)
....for File in Filelist:
........OppFile=open(File,'r')
........FileData=OppFile.readlines()
........for Line in FileData:
............if Line[1]=='l':
................if Line[0]=='X':
....................X=float(Line.split()[1])
................elif Line[0]=='Y':
....................Y=float(Line.split()[1])
................elif Line[0]=='Z':
....................Z=float(Line.split()[1])
........print '%s %.3lf %.3lf %.3lf'%(File.split('.')[0],X,Y,Z)
........OppFile.close()
else: usage()

Now this just prints to the screen and would have to be redirected to a text file. For the fun of it the first modification once we know it is running would be to send it directly to a file. As always, final working code is found on my personal VrPython website.