Read specific area or string in a text file - python-3.x

Question

I have a text file I have written user data to. Username, E-Mail and Password.
That's how the userfile looks like for now
[<< LOGIN >>]
Username: admin
Password: 12345678
E-Mail: hue#hue.hue
[<< LOGIN END >>]
Now for the question.
How can I tell python to specifically read the password only? I mean, it may be possible for now that we know what the password is and what its lenght is. But how am I supposed to read the password later when I encrypt it and get some gibberish with 30+ characters?

Answer 1

The line will contain password so just split once and get the second element:
In [20]: from simplecrypt import encrypt
In [21]: ciph = encrypt('password', "12345678")
In [22]: line = "Password: " + ciph
In [23]: line
Out[23]: 'Password: sc\x00\x01\x0cP\xa1\xee\'$"\xc1\x85\xe0\x04\xd2wg5\x98\xbf\xb4\xd0\xacr\xd3\\\xbc\x9e\x00\xf1\x9d\xbe\xdb\xaa\xe6\x863Om\xcf\x0fc\xdeX\xfa\xa5\x18&\xd7\xcbh\x9db\xc9\xbeZ\xf6\xb7\xd3$\xcd\xa5\xeb\xc8\xa9\x9a\xfa\x85Z\xc5\xb3%~\xbc\xdf'
In [24]: line.split(None,1)[1]
Out[24]: 'sc\x00\x01\x0cP\xa1\xee\'$"\xc1\x85\xe0\x04\xd2wg5\x98\xbf\xb4\xd0\xacr\xd3\\\xbc\x9e\x00\xf1\x9d\xbe\xdb\xaa\xe6\x863Om\xcf\x0fc\xdeX\xfa\xa5\x18&\xd7\xcbh\x9db\xc9\xbeZ\xf6\xb7\xd3$\xcd\xa5\xeb\xc8\xa9\x9a\xfa\x85Z\xc5\xb3%~\xbc\xdf'
In [25]: decrypt("password",line.split(None,1)[1])
Out[25]: '12345678'
In [26]: "12345678" == decrypt("password",line.split(None,1)[1])
Out[26]: True
When you iterate over the file simple use if line.startswith("Password")...
with open(your_file) as f:
for line in f:
if line.startswith("Password"):
password = line.rstrip().split(None,1)[1]
# do your check
You could use a dict and pickle using passwordas a key then just do a lookup:

Answer 2

How can I tell python to specifically read the password only?
data.txt:
[<< LOGIN >>]
Username: admin
Password: 12345678
E-Mail: hue#hue.hue
[<< LOGIN END >>]
[<< LOGIN >>]
Username: admin
Password: XxyYo345320945!##!$##!##$%^%^^##$%!##$#!#41211
E-Mail: hue#hue.hue
[<< LOGIN END >>]
...
import re
f = open('data.txt')
pattern = r"""
Password #Match the word 'Password', followed by...
\s* #whitespace(\s), 0 or more times(*), followed by...
: #a colon
\s* #whitespace, 0 or more times...
(.*) #any character(.), 0 or more times(*). The parentheses 'capture' this part of the match.
"""
regex = re.compile(pattern, re.X) #When you use a pattern over and over for matching, it's more efficient to 'compile' the pattern.
for line in f:
match_obj = regex.match(line)
if match_obj: #then the pattern matched the line
password = match_obj.group(1) #group(1) is what matched the 'first' set of parentheses in the pattern
print password
f.close()
--output:--
12345678
XxyYo345320945!##!$##!##$%^%^^##$%!##$#!#41211
A regular expression (or RE) specifies a set of strings that matches it; the functions in this module let you check if a particular string matches a given regular expression (or if a given regular expression matches a particular string, which comes down to the same thing).
Regular expressions can be concatenated to form new regular expressions; if A and B are both regular expressions, then AB is also a regular expression. In general, if a string p matches A and another string q matches B, the string pq will match AB. This holds unless A or B contain low precedence operations; boundary conditions between A and B; or have numbered group references. Thus, complex expressions can easily be constructed from simpler primitive expressions like the ones described here. For details of the theory and implementation of regular expressions, consult the Friedl book referenced above, or almost any textbook about compiler construction.
A brief explanation of the format of regular expressions follows. For further information and a gentler presentation, consult the Regular Expression HOWTO.
https://docs.python.org/3/library/re.html#module-re