Python – substituting in a file

python

I use python 2.5, i like to replace certain variables in a txt file and write the complete data into new file.

i wrote a program to do the above,

from scipy import *

import numpy 

from numpy import asarray

from string import Template


def Dat(Par):


 Par = numpy.asarray(Par)

 Par[0] = a1

 Par[1] = a2

 Par[2] = a3

 Par[3] = a4

 sTemplate=Template(open('/home/av/W/python/data.txt', 'r').read()).safe_substitute(Par)

 open('/home/av/W/python/data_new.txt' ,'w').write(sTemplate)


Init = numpy.asarray [(10.0, 200.0, 500.0, 10.0)]

Dat(Init)

when i executed the above
*i obtained the error

'TypeError: 'function' object is unsubscriptable'

'data.txt' is a text file, i have placed $a1, $a2, $a3, $a4, i need to replace $a1 $a2 $a3 $a4 by 10.0 200.0 500.0 10.0

My constraints are i need to pass the values only by array like Init = numpy.asarray [(10.0, 200.0, 500.0, 10.0)]

please help me.

is this error due to python 2.5 version? or any mistakes in program

Best Solution

The error is here:

Init = numpy.asarray [(10.0, 200.0, 500.0, 10.0)]

which was probably meant to be

Init = numpy.asarray ([10.0, 200.0, 500.0, 10.0])

(note the swapped braces/parens). Since python found a "[" after "asarray" (which is a function), it throws an error, because you cannot subscribe (i.e. do something like x[17]) a function.

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If the reason you're checking is so you can do something like if file_exists: open_it(), it's safer to use a try around the attempt to open it. Checking and then opening risks the file being deleted or moved or something between when you check and when you try to open it.

If you're not planning to open the file immediately, you can use os.path.isfile

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Starting with Python 3.4, the pathlib module offers an object-oriented approach (backported to pathlib2 in Python 2.7):

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shutil has many methods you can use. One of which is:

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