Develop Reference

How do I load data from a text file in python?

I'm basically writing text to a file for example
data = ("save.data", "a+")
data.write(u"name = 'zrman'")
I wan't to be able to load that file and allow me to do this in python
print name
Any help would be great
-Thx

Use ConfigParser Python module. It's exactely what you're looking for.
Write :
import ConfigParser
config = ConfigParser.RawConfigParser()
config.set('main', 'name', 'zrman')
with open('conf.ini', 'wb') as configfile:
config.write(configfile)
Read :
from ConfigParser import ConfigParser
config = ConfigParser()
config.read('conf.ini')
print config.sections()
# ['main']
print config.items('main')
# [('name', 'zrman')]

Take a look at the docs here, this will walk you through the process of reading and writing files in python.

You could read in the lines and then exec the code:
f = open('workfile', 'w')
for line in f:
exec(line)
print name

working from .txt file to output sha256 hashes in Python

I have created a text file of randomly generated words, now i would like to write a script that can use that data to create sha256 hashes from those words...would prefer for hashes to be saved as a .txt file also, but in my failed attempt here I was simply trying to print them out. Any suggestions?
#!usr/bin/python
# Filename: doesnt_work
import os
import hashlib
with open("wordlist.txt","r") as f:
for line in f:
line = line.rstrip("\n")
m = sha256(line)
print(m.hexdigest())

Although you should have posted the exception, I'm guessing this would fix it
m = hashlib.sha256(line)
And there is an indentation problem
#!usr/bin/python
# Filename: doesnt_work
import os
import hashlib
with open("wl.txt","r") as f:
for line in f.readlines():
line = line.rstrip("\n")
m = hashlib.sha256(line)
print(m.hexdigest())

python search for a string and append to it using regular expression

I need to search for a certain parameter known as jvm_args in a configuration file known as config.ini
**contents of config.ini:
first_paramter=some_value1
second_parameter=some_value2
jvm_args=some_value3**
I need to know how to find this parameter in my file and append something to its value, (i.e append a string to the string some_value3).

If you "just" want to find keys and values in an ini file, I think the configparser module is a better bet than using regexps. The configparser asserts that the file has "sections", though.
Documentation for configparser is here: http://docs.python.org/library/configparser.html - useful examples at the bottom. The configparser can also be used for setting values and writing out a new .ini-file.
Input file:
$ cat /tmp/foo.ini
[some_section]
first_paramter = some_value1
second_parameter = some_value2
jvm_args = some_value3
Code:
#!/usr/bin/python3
import configparser
config = configparser.ConfigParser()
config.read("/tmp/foo.ini")
jvm_args = config.get('some_section', 'jvm_args')
print("jvm_args was: %s" % jvm_args)
config.set('some_section', 'jvm_args', jvm_args + ' some_value4')
with open("/tmp/foo.ini", "w") as fp:
config.write(fp)
Output file:
$ cat /tmp/foo.ini
[some_section]
first_paramter = some_value1
second_parameter = some_value2
jvm_args = some_value3 some_value4

You can use re.sub
import re
import os
file = open('config.ini')
new_file = open('new_config.ini', 'w')
for line in file:
new_file.write(re.sub(r'(jvm_args)\s*=\s*(\w+)', r'\1=\2hello', line))
file.close()
new_file.close()
os.remove('config.ini')
os.rename('new_config.ini', 'config.ini')
also check ConfigParser

As both avasal and tobixen have suggested, you can use the python ConfigParser module to do this. For example, I took this "config.ini" file:
[section]
framter = some_value1
second_parameter = some_value2
jvm_args = some_value3**
and ran this python script:
import ConfigParser
p = ConfigParser.ConfigParser()
p.read("config.ini")
p.set("section", "jvm_args", p.get("section", "jvm_args") + "stuff")
with open("config.ini", "w") as f:
p.write(f)
and the contents of the "config.ini" file after running the script was:
[section]
framter = some_value1
second_parameter = some_value2
jvm_args = some_value3**stuff

without regex you can try:
with open('data1.txt','r') as f:
x,replace=f.read(),'new_entry'
ind=x.index('jvm_args=')+len('jvm_args=')
end=x.find('\n',ind) if x.find('\n',ind)!=-1 else x.rfind('',ind)
x=x.replace(x[ind:end],replace)
with open('data1.txt','w') as f:
f.write(x)

Getting doc string of a python file

Is there a way of getting the doc string of a python file if I have only the name of the file ? For instance I have a python file named a.py. I know that it has a doc string ( being mandated before) but don't know of its internal structure i.e if it has any classes or a main etc ? I hope I not forgetting something pretty obvious
If I know it has a main function I can do it this way that is using import
filename = 'a.py'
foo = __import__(filename)
filedescription = inspect.getdoc(foo.main())
I can't just do it this way:
filename.__doc__ #it does not work

You should be doing...
foo = __import__('a')
mydocstring = foo.__doc__
or yet simpler...
import a
mydocstring = a.__doc__

import ast
filepath = "/tmp/test.py"
file_contents = ""
with open(filepath) as fd:
file_contents = fd.read()
module = ast.parse(file_contents)
docstring = ast.get_docstring(module)
if docstring is None:
docstring = ""
print(docstring)

And if you need the docstrings of the module your are already in :
import sys
sys.modules[__name__].__doc__

Replace a whole line in a txt file

I'am new to Python 3 and could really use a little help. I have a txt file containing:
InstallPrompt=
DisplayLicense=
FinishMessage=
TargetName=D:\somewhere
FriendlyName=something
I have a python script that in the end, should change just two lines to:
TargetName=D:\new
FriendlyName=Big
Could anyone help me, please? I have tried to search for it, but I didnt find something I could use. The text that should be replaced could have different length.

import fileinput
for line in fileinput.FileInput("file",inplace=1):
sline=line.strip().split("=")
if sline[0].startswith("TargetName"):
sline[1]="new.txt"
elif sline[0].startswith("FriendlyName"):
sline[1]="big"
line='='.join(sline)
print(line)

A very simple solution for what you're doing:
#!/usr/bin/python
import re
import sys
for line in open(sys.argv[1],'r').readlines():
line = re.sub(r'TargetName=.+',r'TargetName=D:\\new', line)
line = re.sub(r'FriendlyName=.+',r'FriendlyName=big', line)
print line,
You would invoke this from the command line as ./test.py myfile.txt > output.txt

Writing to a temporary file and the renaming is the best way to make sure you won't get a damaged file if something goes wrong
import os
from tempfile import NamedTemporaryFile
fname = "lines.txt"
with open(fname) as fin, NamedTemporaryFile(dir='.', delete=False) as fout:
for line in fin:
if line.startswith("TargetName="):
line = "TargetName=D:\\new\n"
elif line.startswith("FriendlyName"):
line = "FriendlyName=Big\n"
fout.write(line.encode('utf8'))
os.rename(fout.name, fname)

Is this a config (.ini) file you're trying to parse? The format looks suspiciously similar, except without a header section. You can use configparser, though it may add extra space around the "=" sign (i.e. "TargetName=D:\new" vs. "TargetName = D:\new"), but if those changes don't matter to you, using configparser is way easier and less error-prone than trying to parse it by hand every time.
txt (ini) file:
[section name]
FinishMessage=
TargetName=D:\something
FriendlyName=something
Code:
import sys
from configparser import SafeConfigParser
def main():
cp = SafeConfigParser()
cp.optionxform = str # Preserves case sensitivity
cp.readfp(open(sys.argv[1], 'r'))
section = 'section name'
options = {'TargetName': r'D:\new',
'FriendlyName': 'Big'}
for option, value in options.items():
cp.set(section, option, value)
cp.write(open(sys.argv[1], 'w'))
if __name__ == '__main__':
main()
txt (ini) file (after):
[section name]
FinishMessage =
TargetName = D:\new
FriendlyName = Big

subs_names.py script works both Python 2.6+ and Python 3.x:
#!/usr/bin/env python
from __future__ import print_function
import sys, fileinput
# here goes new values
substitions = dict(TargetName=r"D:\new", FriendlyName="Big")
inplace = '-i' in sys.argv # make substitions inplace
if inplace:
sys.argv.remove('-i')
for line in fileinput.input(inplace=inplace):
name, sep, value = line.partition("=")
if name in substitions:
print(name, sep, substitions[name], sep='')
else:
print(line, end='')
Example:
$ python3.1 subs_names.py input.txt
InstallPrompt=
DisplayLicense=
FinishMessage=
TargetName=D:\new
FriendlyName=Big
If you are satisfied with the output then add -i parameter to make changes inplace:
$ python3.1 subs_names.py -i input.txt