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Reverse Data File

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Join Date: Jun 2007

Posts: 1

Reputation: cameyo is an unknown quantity at this point

Solved Threads: 0

cameyo

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Newbie Poster

Reverse Data File

Jun 28th, 2007

I have a delimited text file with some data.
I need to revert the data in this way:
1) the last line will be the first, and son on (invert all the lines)
2) each line must have a reverted data (last data item will be the first and so on)

Example:
file IN:
100 200 230
238 345 333
234 455 248

file OUT
248 455 234
333 345 238
230 200 100

can you help me ?

Thanks in advance

cameyo

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Join Date: May 2007

Posts: 15

Reputation: ffao is an unknown quantity at this point

Solved Threads: 4

ffao

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Newbie Poster

Re: Reverse Data File

Jun 28th, 2007

First, I have to tell you that the data will be separated by one space only, regardless of how many there were in the original file. This is a simple code which has no concerns whatsoever with memory/speed, as it keeps the whole file in memory.

 Help with Code Tags 
 python Syntax (Toggle Plain Text) 
inp = open("somefile", "r")
out = open("anotherfile", "w")
 
out.write("\n".join(" ".join(reversed(i.rstrip().split())) for i in reversed(inp.readlines())))
 
inp.close()
out.close()
inp = open("somefile", "r")
out = open("anotherfile", "w")

out.write("\n".join(" ".join(reversed(i.rstrip().split())) for i in reversed(inp.readlines())))

inp.close()
out.close()

The fourth line is the one that does the job. Here it is, in a more friendly code block:

 Help with Code Tags 
 python Syntax (Toggle Plain Text) 
#we will produce each line one by one and store here
result = []
 
for i in reversed(inp.readlines()): # get the lines in reverse fashion
    i = i.rstrip() # strip trailing newline
    # split the data into a list, then reverse the order and join back with one space separating data
    string = " ".join(reversed(i.split())) 
    #the line is correct, add it to the list
    result.append(string)
 
#join all of the lines, inserting a newline in-between
write_str = "\n".join(result)
 
#write
out.write(write_str)
#we will produce each line one by one and store here
result = []

for i in reversed(inp.readlines()): # get the lines in reverse fashion
    i = i.rstrip() # strip trailing newline
    # split the data into a list, then reverse the order and join back with one space separating data
    string = " ".join(reversed(i.split())) 
    #the line is correct, add it to the list
    result.append(string)

#join all of the lines, inserting a newline in-between
write_str = "\n".join(result)

#write
out.write(write_str)