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In python, I want to open a file if already exists or create it if it doesnt exist. also i want to write to the file new contents on opening it without overwriting the existing contents of the file. How can I do it?
PEP8 suggests you to use:
with open('test.txt', 'a+') as f:
f.write( "Your new content" )
The with statement is better because it will ensure you always close the file, even if an exception is raised.
Example adapted from: http://docs.python-guide.org/en/latest/writing/style/#pep-8
You can use:
file = open('myfile.dat', 'a+')
Refer to this link for details:
http://docs.python.org/2/tutorial/inputoutput.html
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I am Python newbie and I am trying to learn how to parse files but I really don't even know where to begin. I need to basically find a specific code inside the code to confirm the functionality of the run log supplied to me. I just need help in the steps to: Open a file, parse a file, and close a file on Python. If you need anymore info please let me know. I can't supply the code but I can try to give as much info as I can. Thanks!
Opening a file:
myLog = open("path/to/my/log", 'r')
Loop through the lines:
for line in myLog:
if foundMyThing(line):
print "Found it!"
Close it:
myLog.close()
Read the docs:
https://docs.python.org/2/tutorial/inputoutput.html#reading-and-writing-files
with open("myfile.myextension",r) as f:
for line in f:
<parse each line>
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There were some other questions that were similar but none of them answered my question. I need a simple way to assign a different variable to each line, so I can use it later on.
Please keep it simple, it's for my controlled assessment and I need to remember all of it.
No, you absolutely do not want to do this. There is never any reason to be assigning an unknown number of variables.
You assign a single variable, a list, with each element equal to a line:
f = open('myfile.text')
contents = f.readlines()
although most likely, since that will include the newline character at the end of the line, you want to strip it off first:
contents = [line.strip() for line in f]
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I am aware that you can use the pwd module on python to extract passwd structures for use; however, my question is as such:
if I read into my program a line such as
blah1:tVNIsQ0yDrLxM:16009:0:99999:7:::
or
blah2:$6$WVsjYh8e$5r2wvIaeiFI6CCFRw6stfbah0Q.wrcKITdmEDCvG2cNC4fXkVbgRiOdeCdU.WeD1NIyzLh/sXycXQFEQcNWsv/:16009:0:99999:7:::
how would I read just the section that reads "tVNIsQ0yDrLxM"?
Thank you
As long as there's no extra colons in there, this should work:
password = hash.split(':')[1]
split
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in order to do some operations with it but I would like to do it from an interface in order to select the file instead of just running a script with the name of the file, as the file name will change every day.
You can use Tkinter askopenfilename :
from tkFileDialog import askopenfilename
path = askopenfilename()
f = open(path, 'r') # OR DO WHAT YOU WANT WITH PATH
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I have a folder of CSV files that I need to edit. Each file has a blank line in the middle. I want to take everything under that blank line and put it into a new excel sheet while rewriting my CSV file to a xls file. How can I do this?
A quick Google search revealed the openpyxl library that you can use to create XLS files.
Reading CSV is built into Python.
The rest is a simple matter of programming :) If you run into a more specific problem, please feel free to post a new question.