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how can i make store a username in txt file without having the same username twice?

user = input("\nInput user's Login ID: ")
while True:
password = str(input ("Input user's Password: "))
rpass = str(input("Re-enter the Password: "))
if password == rpass:
file = open("username.txt", "a")
file.write (user)
file.close()
break
else:
print("You have entered the wrong password, Try Again")
I want make a program where users can sign up with their username and password and it can be stored into a txt file. And the next person that is going to sign up won't be able to use the same username.
I renewed the code but the same problem happened, the previous username is not detected.

Every time you write to the file, it appends to the same line.
if data == user+ ":" +password:
This condition is never true as a result.
One possible solution is to add \n after every write.
file.write (user +" : "+ password +"\n")
And your condition would be
if data == user+ " : " +password:
Be mindful of whitespaces and other characters. It should be an exact match with this method.
Edit: You're checking whether the new username and password together are a match.
What you should be doing is matching user with data.split(':')[0][:-1] -
if data.split(":")[0][:-1] == user
This will collect the string till the ':' and truncate the trailing space.

If you want to use the parse module, you can run pip install parse and use this code:
import parse
pattern = '{[a-z][A_Z][0-9]} : {[a-z][A_Z][0-9]}'
lines = []
user = input ("enter username: ")
password = input ("enter password: ")
with open('username.txt', 'r') as f:
line = f.readline()
while line:
u, p = parse.parse(pattern, line)
lines.append((u, p))
line = f.readline()
users = [ u for (u, p) in lines ]
if user in users:
print(f'Username {user} is taken, please try again.')
else:
with open('username.txt', 'a') as f:
f.write(f'{user} : {password}')
print(f'Username and password successfully created.')

Python - Read each line of text file and pass each line to variable

I am attempting to implement a simple password checker which will allow the user to open a text file that contains generated passwords and check them against a list of criteria to see if the password is strong or weak. It should then output the password with the result of whether it is strong or weak.
With the current solution I can get the list of passwords to print, but when the check as to whether the password is strong or not, only one result is shown. I am attempting for the output to be the password that is generated with the result e.g. Randompassword123 - This is a weak password.
Below is the code I am currently using:
def multiplestrength(): # password strength check function
textfile = filedialog.askopenfilename(initialdir="/home", title = "Select text file to split",filetypes = (("text files","*.txt"),("all files","*.*")))
with open(textfile , mode="r",encoding="utf-8") as my_file:
data=my_file.read()
print(data)
def strongPassword(data):
if passRegex1.search(data) == None:
return False
if passRegex2.search(data) == None:
return False
if passRegex3.search(data) == None:
return False
if passRegex4.search(data) == None:
return False
else:
return True
passRegex1 = re.compile(r'\w{8,}')
passRegex2 = re.compile(r'\d+')
passRegex3 = re.compile(r'[a-z]')
passRegex4 = re.compile(r'[A-Z]')
if strongPassword(data) == True:
print("Strong Password")
else:
print("This is not a strong password")
The output I receive is below
So it appears that only one password is being checked from the list of 5 passwords in the text file. I believe there might need to be a for loop required somewhere for each password to be checked, but I am unsure what way to approach this. Another approach I was thinking would be to insert the passwords from the text file into a list and iterating through this list to get a result for each password. Does this possibly sound like the correct way to approach this?
Any help with this would be greatly appreciated.
Thanks

I have written a solution. I have added many comment for code as description.
Code:
import re
passRegex1 = re.compile(r'\w{8,}')
passRegex2 = re.compile(r'\d+')
passRegex3 = re.compile(r'[a-z]')
passRegex4 = re.compile(r'[A-Z]')
def strong_password(data): # the function name should be snake case
if not passRegex1.search(data): # Use "if not". It is the Pythonic way. It handles False/None/0/""/[] etc...
return False
if not passRegex2.search(data):
return False
if not passRegex3.search(data):
return False
if not passRegex4.search(data):
return False
else:
return True
with open("test.txt", mode="r", encoding="utf-8") as my_file: # Open file for reading
for line in my_file.readlines(): # Read all lines one-by-one
print("\nPassword: {}".format(line.strip())) # Print the current password ("strip" removes the whitespace characters from string).
if strong_password(line): # This statement is True if the "strong_password" function returns True
print("Strong Password")
continue # Get the next element (line of file)
print("This is not a strong password") # Else statement is not needed because the "if" contains a continue
My test file:
asdf
121234
adsf123
asdffdsatre323423
fdggfd2323____,,,**
tt
333345
asdfSDFGRAdsfAERTGRghRGads___++((((FDsaSDfAS4233423524
434
55555
Output:
>>> python3 test.py
Password: asdf
This is not a strong password
Password: 121234
This is not a strong password
Password: adsf123
This is not a strong password
Password: asdffdsatre323423
This is not a strong password
Password: fdggfd2323____,,,**
This is not a strong password
Password: tt
This is not a strong password
Password: 333345
This is not a strong password
Password: asdfSDFGRAdsfAERTGRghRGads___++((((FDsaSDfAS4233423524
Strong Password
Password: 434
This is not a strong password
Password: 55555
This is not a strong password

You could loop through the lines of your file using:
with open(textfile , mode="r",encoding="utf-8") as my_file:
for line in my_file:
# do something with the line, eg:
if strongPassword(line):
# ...
Edit: you might want to use line.strip() instead of line to get rid of the newline characters at the end (\n)

How to read external file in python?

i need to be able to save and get usernames and passwords from an external file. this is what i have done so far however it constantly says that username or password is incorrect even when i enter it correctly. does anyone know how to fix this problem.
this is my current code
import time
print("Welcome...")
welcome = input("Do you have an acount? y/n: ")
if welcome == "n":
while True:
username = input("Enter a username:")
password = input("Enter a password:")
password1 = input("Confirm password:")
if password == password1:
file = open("gcsetask.txt", "a")
file.write(username + ":" + password)
file.write('\n')
file.close()
welcome = "y"
time.sleep(0.4)
print("now lets login")
break
print("Passwords do NOT match!")
if welcome == "y":
while True:
login1 = input("Enter username:")
login2 = input("Enter Password:")
file = open("gcsetask.txt", "r")
data = file.readlines()
file.close()
if data == (login1 + ":" + login2):
print("Welcome")
break
print("Incorrect username or password.")

Three methods to read a file
read() It returns the read bytes in form of a string.
fileObject.read()
You can also define, how many bytes to read by
`fileObject.read([n]) //If n is not define, it will read the whole file`
readline([n]) It reads the line and return in the form of string, It only read single line
fileObject.readline([n])
readlines() It reads all the lines of the file and return each line a string element in a list
fileObject.readlines()
Hope it helps

I have changed the code to look at each line of that file. Allowing multiple users.
import time
print("Welcome...")
welcome = input("Do you have an acount? y/n: ")
if welcome == "n":
while True:
username = input("Enter a username:")
password = input("Enter a password:")
password1 = input("Confirm password:")
if password == password1:
file = open("gcsetask.txt", "a")
file.write(username+":"+password)
file.write('\n')
file.close()
welcome = "y"
time.sleep(0.4)
print("now lets login")
break
print("Passwords do NOT match!")
if welcome == "y":
while True:
login1 = input("Enter username:")
login2 = input("Enter Password:")
file = open("gcsetask.txt", "r")
data = file.readlines()
file.close()
for line in data:
if line == (login1+":"+login2+"\n"):
print("Welcome")
break
else:
print("Incorrect username or password.")

The function readlines() saves each line in a string inside a list.
If a file contains-
first line
second line
readlines() gives: ['first line','second line']
Try accessing them using index such as data[0] and data[1]

When you use file.readlines(), the function returns a list of all lines in the file. Thus, when you define data as:
data = file.readlines()
if you print(data), you get something similar to:
['user:pass\n'] # note the the \n at the end
Then, in the following line:
if data == (login1+":"+login2):
you're trying to compare a string (login1+":"+login2) with a list, which is always False because they have different type.
Changing the condition to:
if login1+":"+login2 in data:
should fix this problem (but you'll have a different one, see below).
About the trailing \n:
file.readlines() splits the lines in a list, but does not remove the newline character. This will cause your test to still fail always, because you don't account for it in the test.
Possible solutions are:
1) include the \n in the string you search:
if '{}:{}\n'.format(login1,login2) in data:
2) read the whole file and use splitlines instead, which will remove the newline characters
data = file.read().splitlines()

The readlines method returns the list of lines which you need to iterate on it to find the appropriate login information.
data = file.readlines()
login_info = f"{login1}:{login2}\n"
if login_info in data:
print("Welcome")
break
And also you can remove \n from the end of each line using splitlines.
data = file.read().splitlines()
login_info = f"{login1}:{login2}"
if login_info in data:
print("Welcome")
break
And another alternative is remove \n from parsed lines manually.
data = [line.rstrip('\n') for line in file.readlines()]
login_info = f"{login1}:{login2}"
if login_info in data:
print("Welcome")
break

if block doesn't trigger, even when it should

Clearly I'm doing something wrong here...
accountManager = open("accountManager.txt","r")
userNameInvalid = True
while userNameInvalid == True:
userName = input("Username (this is public): ")
userNameLine = 0
for line in accountManager.readlines():
if (((userNameLine % 6) == 2) and (userName == line)):
print("The username \"" + userName + "\" taken, please choose another one.")
userNameInvalid = True
break
userNameInvalid = False
userNameLine += 1
For context: accountManager is a txt file (currently open in 'r' mode) that looks like the following:
*empty line*
Real name 1
Username 1
Email 1
Notes 1
*empty line*
*empty line*
Real name 2
Username 2
Email 2
Notes 2
*empty line*
*empty line*
Real name 3
Username 3
Email 3
Notes 3
*empty line*
As you can see, it comes in little "chunks" of 6 lines, the number of which would be unknown.
What I want it to do:
Only when the input is "Username 1", "Username 2" or "Username 3", the if statement should trigger.
What happens:
if statement never runs
UPDATE:
If statement now runs, but now, if you at first enter a taken username, it will get stuck in the while loop and never get out... Why?

It's because of the condition userName == line is never true. When you read a line using f.read(), or f.readlines(), each line is terminated with the new line character \n. So, for example, instead of "Username 1", the line will be "Username 1\n". A simple way to solve this is to append "\n" to the comparison string userName as the following.
userName = input("Username (this is public): ") + "\n"
Also, f.readlines() returns an empty list if you don't reset the file object. You can get stuck in the while loop as the result. You can fix it using f.seek(0), but instead of re-reading the file multiple times, save the list of lines for re-use.
accountManager = open("accountManager.txt","r")
userNameInvalid = True
lines = accountManager.readlines()
while userNameInvalid == True:
userName = input("Username (this is public): ")
userNameLine = 0
for line in lines:
if userNameLine % 6 == 2 and userName == line:
print("The username \"" + userName + "\" taken, please choose another one.")
userNameInvalid = True
break
userNameInvalid = False
userNameLine += 1

As you have it the code is hard to follow. I would restructure the code by first reading all the data into a more usable format, and only then validate it. You can take each section of user data and place them into a list of small dicts.
Using a while loop and iter/next you could pretty easily parse the data. You should also strip the line to remove extra whitespace:
raw_data = iter(accountManager.readlines())
user_data = []
try:
while True:
next(raw_data) # clear blank line
user_data.append(
{
'real_name': next(raw_data).strip(),
'username': next(raw_data).strip(),
'email': next(raw_data).strip(),
'notes': next(raw_data).strip(),
}
)
next(raw_data) # clear blank line
except StopIteration: # no more values in raw_data iter
pass # do nothing, we expect this
Once you have the data, I would use a set to check for duplicates:
username_invalid = False
usernames = set()
for data in user_data:
username = data['username']
if username in usernames:
print(
f'The username "{username}" '
'is taken, please choose another one.'
)
username_invalid = True
break
usernames.add(username)

Command only reads first line of text file

I have to make a program in which one of the functions is retrieval of usernames and results from a text file. (All on the same line)
For some reason, when I run it, only the first line is printed out. Why is this ? Also, this only happens when I try to run the program at school (part of an assignment), it prints everything it needs to on my laptop at home. (Python versions are also the same)
Here is my code :
def results():
username = input("Enter username :")
for line in open("resultsfile.txt","r"):
if username in line:
print (line)
elif username not in line:
("No such user")
Also, this is what the text file looks like (without bullet points) :
tud16 CS Easy 2points
ser23 CH Med 4points
tud16 CS Hard 1points

def results():
username = input("Enter username :")
for line in open("resultsfile.txt","r"):
if username in line:
print (line)
else:
print("No such user")
results()

You are iterating over a file but you are printing No such user for every line that does not match the username.
What you should do is evaluate after the loop if one of the lines in the file contained the username. To implement this you could introduce a boolean (found) indicating if a user has been found or not:
def results():
found = False
username = input("Enter username :")
for line in open("resultsfile.txt","r"):
if username in line:
print (line)
found = True
if not found:
print("No such user")