我不明白为什么我不能让 python 中的 readline function 在这个程序中工作。 我究竟做错了什么？

Question

In this program I want to save individual lines to a variable but when i try to print the variable it just returns a space instead of whats on the line in the file. sorry i'm quite new to programming

file=open('emails.txt','w+')
while True:

    email=input('pls input your email adress: ')
    file.write(email)
    file.write('\n')
    more=input('would you like more emails to be processed? ')
    if more == 'yes' or more == 'ye' or more == 'y' or more == 'yep' or more == 'Y':
        continue

    elif more == 'no' or more == 'nah' or more == 'n' or more == 'N' or more == 'nope':
        file.close()
        print('this is the list of emails so far')
        file=open('emails.txt','r')
        print(file.read()) #this reads the whole file and it works
        email_1=file.readline(1) #this is meant to save the 1st line to a variable but doesn't work!!!
        print(email_1) #this is meant to print it but just returns a space
        file.close()
        print('end of program')

Answer 1

First, you should use with to work with files.

Second, you open the file for printing and read all of its content: print(file.read())

after this line, the cursor is in the end of the file, so next time you try to read something from the file, you get empty string.

to fix it, you have few alternatives.

First option:

add file.seek(0, 0) to move the cursor back to the start of the file so when you do file.readline , you will realy read the file line.

moreover, file.readline(1) should be changed to file.readline()

Second option:

just read all the file content into a list, print it and then print the first entry in the list(the first line in the file...)

file = open('emails.txt', 'r')
content = file.readlines()
print(*content, sep='')
email_1 = content[0] 
print(email_1)  

Answer 2

As mentioned in the first comment above, the file.read() call is moving your file pointer to the end of the file, so there is no data left for the readline() to read.

But also, you are calling readline(1) which will read one byte, not one line.

Answer 3

Well I would try to use with

So try to implement it like this:

> with open('emails.txt','w+') as output_file:  
   while True:
    # and then rest of your code