Reading and writing variables from file - file

Question

I'm trying to create a register/login CLI and I don't understand why don't the variables I write inside the register file work later when I try to use them in the login part.
I thought it was as easy as writing abc="xyz" and then reading that file, but it seems it's not like that.
###RegOrLog###
RegOrLog = str(raw_input('[Register/Log]:'))
###register the user detail###
if RegOrLog in('r', 'reg', 'register'):
reguser = raw_input('username:')
regpass = raw_input('password:')
regage = int(raw_input('age:'))
reggender = str(raw_input('gender:'))
###creating file for the user###
f = open(reguser, 'w')
f.write('password =' + repr(regpass) + '\n')
f.write('age =' + repr(regage) + '\n')
f.write('gender =' + repr(reggender) + '\n')
f.close()
RegOrLog = 'log'
###login as a user###
if RegOrLog in('l','log','login'):
loguser = raw_input('Login username:')
regpass = raw_input('password:')
#registered user#
regeduser = open(loguser, 'r')
regeduser = regeduser.read()
if regpass == password:
print 'Welcome', loguser
print 'You are', gender
print 'You are', age,'years old'

Answer 1

I now understand your problem. A text file just saves plain data, therefore, you cannot create a file writing like if it were a Python file, with a variable definition, and expect that when you read the file again all those variables will be initialized. Python will only read the data and assign it to a variable which will contain all the text you originally wrote into that file.
So, summing up, you are treating a text file like a python file and expecting python to execute the text file and create a variable.
But that does not work like that. You have to store the data in a database-like file (or in a database itself), then read it, and by means of data parsing, extract the variables you had written into the text file before.
You can do that manually, which is not very nice, or you can use a Python module called Pickle, which handles pretty much everything you would write yourself, and so you would only have to make use of this module in your code.
If you search for the Pickle module in Google, the Python.org website provides a very nice example of its usage:
#Pickle Example
# Save a dictionary into a pickle file.
import pickle
favorite_color = { "lion": "yellow", "kitty": "red" }
pickle.dump( favorite_color, open( "save.p", "wb" ) )
# Load the dictionary back from the pickle file.
favorite_color = pickle.load( open( "save.p", "rb" ) )
# favorite_color is now { "lion": "yellow", "kitty": "red" }
So, how would you use it in your code? This easy:
# RegOrLog
import pickle # new line!
RegOrLog = raw_input('[Register/Log]:') # why str()?
# register the user detail
if RegOrLog in('r', 'reg', 'register'):
reguser = raw_input('username:') # raw_input gives string by default, if you want other data type then you do have to convert it.
regpass = raw_input('password:')
regage = int(raw_input('age:'))
reggender =raw_input('gender:')
# creating file for the user
data = {"username": reguser, "password": regpass, "age": regage, "gender": reggender}
pickle.dump( data, open( "whatever_file_name", "wb" ) )
RegOrLog = 'log'
###login as a user###
if RegOrLog in('l','log','login'):
loguser = raw_input('Login username:')
regpass = raw_input('password:')
#registered user#
data = pickle.load( open( "whatever_file_name", "rb" ) )
if regpass == data["password"]:
print 'Welcome', loguser
print 'You are', gender
print 'You are', age,'years old'