Search for values in all text files and multiply them by fixed value ? (in PYTHON ?)

Question

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Hi friends.

I have a lot of files, which contains text information, but I want to search only specific lines, and then in these lines search for on specific position values and multiply them with fixed value (or entered with input).

Example text:

1,0,0,0,1,0,0
15.000,15.000,135.000,15.000
7
3,0,0,0,2,0,0
'holep_str',50.000,-15.000,20.000,20.000,0.000
3
3,0,0,100,3,-8,0
58.400,-6.600,'14',4.000,0.000
4
3,0,0,0,3,-8,0
50.000,-15.000,50.000,-15.000
7
3,0,0,0,4,0,0
'holep_str',100.000,-15.000,14.000,14.000,0.000
3
3,0,0,100,5,-8,0
108.400,-6.600,'14',4.000,0.000

And I want to identify and modify only lines with "holep_str" text:

'holep_str',50.000,-15.000,20.000,20.000,0.000
'holep_str',100.000,-15.000,14.000,14.000,0.000

There are in each line that begins with the string "holep_str" two numbers, at position 3rd and 4th value:

20.000 20.000
14.000 14.000

And these can be identified like:
1./ number after 3rd comma on line beginning with "holep_str"
2./ number after 4th comma on line beginning with "holep_str"

RegEx cannot help, Python probably sure, but I'm in time press - and go no further with the language...

Is there somebody that can explain how to write this relative simple code, that finds all lines with "search string" (= "holep_str") - and multiply the values after 3rd & 4th comma by FIXVALUE (or value input - for example "2") ?

The code should walk through all files with defined extension (choosen by input - for example txt) where the code is executed - search all values on needed lines and multiply them and write back...

So it looks like - if FIXVALUE = 2:
'holep_str',50.000,-15.000,40.000,40.000,0.000
'holep_str',100.000,-15.000,28.000,28.000,0.000

And whole text looks like then:
1,0,0,0,1,0,0
15.000,15.000,135.000,15.000
7
3,0,0,0,2,0,0
'holep_str',50.000,-15.000,40.000,40.000,0.000
3
3,0,0,100,3,-8,0
58.400,-6.600,'14',4.000,0.000
4
3,0,0,0,3,-8,0
50.000,-15.000,50.000,-15.000
7
3,0,0,0,4,0,0
'holep_str',100.000,-15.000,28.000,28.000,0.000
3
3,0,0,100,5,-8,0
108.400,-6.600,'14',4.000,0.000

Thank You.

Answer 1

with open(file_path) as f:
    lines = f.readlines()

for line in lines:
    if line.startswith(r"'holep_str'"):
        split_line = line.split(',')
        num1 = float(split_line[3])
        num2 = float(split_line[4])
        print num1, num2
        # do stuff with num1 and num2

Once you .split() the lines with the argument ,, you get a list. Then, you can find the values you want by index, which are 3 and 4 in your case. I also convert them to float at the end.

Answer 2

Also final solution - whole program (version: python-3.6.0-amd64):

# import external functions / extensions ...
import os  
import glob

# functions definition section
def fnc_walk_through_files(path, file_extension):
   for (dirpath, dirnames, filenames) in os.walk(path):
      for filename in filenames:
         if filename.endswith(file_extension): 
            yield os.path.join(path, filename)

# some variables for counting
line_count = 0

# Feed data to program by entering them on keyboard
print ("Enter work path (e.g. d:\\test) :")
workPath = input( "> " )
print ("File extension to perform Search-Replace on [spf] :")
fileExt = input( "> " )
print ("Enter multiplier value :")
multiply_value = input( "> " )
print ("Text to search for :")
textToSearch = input( "> " ) 

# create temporary variable with path and mask for deleting all ".old" files
delPath = workPath + "\*.old"
# delete old ".old" files to allow creating backups
for files_to_delete in glob.glob(delPath, recursive=False):
    os.remove(files_to_delete)

# do some needed operations...
print("\r") #enter new line
multiply_value = float(multiply_value) # convert multiplier to float
textToSearch_mod = "\'" + textToSearch # append apostrophe to begin of searched text
textToSearch_mod = str(textToSearch_mod) # convert variable to string for later use
# print information line of what will be searched for
print ("This is what will be searched for, to identify right line: ", textToSearch_mod)
print("\r") #enter new line

# walk through all files with specified extension <-- CALLED FUNCTION !!!
for fname in fnc_walk_through_files(workPath, fileExt):
   print("\r") # enter new line
   # print filename of processed file
   print("          Filename processed:", fname )
   # and proccess every file and print out numbers
   # needed to multiplying located at 3rd and 4th position
   with open(fname, 'r') as f: # opens fname file for reading
       temp_file = open('tempfile','w') # open (create) tempfile for writing
       lines = f.readlines() # read lines from f:
       line_count = 0 # reset counter
       # loop througt all lines
       for line in lines:
           # line counter increment
           line_count = line_count + 1
           # if line starts with defined string - she will be processed
           if line.startswith(textToSearch_mod):
               # line will be divided into parts delimited by ","
               split_line = line.split(',')
               # transfer 3rd part to variable 1 and make it float number
               old_num1 = float(split_line[3])
               # transfer 4th part to variable 2 and make it float number
               old_num2 = float(split_line[4])
               # multiply both variables
               new_num1 = old_num1 * multiply_value
               new_num2 = old_num2 * multiply_value
               # change old values to new multiplied values as strings
               split_line[3] = str(new_num1)
               split_line[4] = str(new_num2)
               # join the line back with the same delimiter "," as used for dividing
               line = ','.join(split_line)
               # print information line on which has been the searched string occured
               print ("Changed from old:", old_num1, old_num2, "to new:", new_num1, new_num2, "at line:", line_count)
               # write changed line with multiplied numbers to temporary file
               temp_file.write(line)
           else:
               # write all other unchanged lines to temporary file
               temp_file.write(line)
   # create new name for backup file with adding ".old" to the end of filename
   new_name = fname + '.old'
   # rename original file to new backup name
   os.rename(fname,new_name)
   # close temporary file to enable future operation (in this case rename)
   temp_file.close()
   # rename temporary file to original filename
   os.rename('tempfile',fname)

Also after 2 days after asking with a help of good people and hard study of the language :-D (indentation was my nightmare) and using some snippets of code on this site I have created something that works... :-) I hope it helps other people with similar question...

At beginning the idea was clear - but no knowledge of the language...

Now - all can be done - only what man can imagine is the border :-)

I miss GOTO in Python :'( ... I love spaghetti, not the spaghetti code, but sometimes it would be good to have some label<--goto jumps... (but this is not the case...)