如何在python中迭代readlines（）

Question

I am trying to add lines from a txt file to a python list for iteration, and the script wants to print every line and return an error. I'm using the readlines() function, but when I use list.remove(lines), it returns an error: File "quotes.py", line 20, in main list.remove(lines) TypeError: remove() takes exactly one argument (0 given).

def main():
while True:
    try:
        text_file = open("childrens-catechism.txt", "r")
        lines = text_file.readlines()
        #    print lines
        #    print len(lines)
        if len(lines) > 0:
            print lines
            list.remove(lines)
            time.sleep(60)
        else:
            print "No more lines!"
        break
        text_file.close()

I can't see what I'm doing wrong. I know it has to do with list.remove(). Thank you in advance.

Answer 1

You can write in this way. It will save you some time and give you more efficiency.

import time
def main():
    with open("childrens-catechism.txt", "r") as file:
        for line in file:
            print line,
            time.sleep(60)

Answer 2

lines is a list here from your txt. files, and list.remove(lines) is not a correct syntax, you trying to delete a list on list. list is a function in Python. You can delete the elements in lines like;

del lines[0]
del lines[1]
...

or

lines.remove("something")

The logic is, remove() is deleting an element in a list, you have to write that list before remove() after then you have to write the thing that you want to delete in paranthesis of remove() function.

Answer 3

Try this as per your requirements, this will do what you need.

import time
def main():
    with open("childrens-catechism.txt", "r") as file:
        for lines in file.readlines():
            if len(lines) > 0:
                for line in lines:
                    print line
                    lines.remove(line)
            else:
                print "No more lines to remove"
            time.sleep(60)

Answer 4

On opening a file, we can convert the file lines onto a list,

lines = list(open("childrens-catechism.txt", "r"))

From this list we can now remove entries with length greater than zero, like this,

for line in lines:
    if len(line) > 0:
            # do sth
            lines.remove(line)

Answer 5

If you are trying to read all the lines from the file and then print them in order, and then delete them after printing them I would recommend this approach:

    import time

    try:
        file = open("childrens-catechism.txt")
        lines = file.readlines()

        while len(lines) != 0:
            print lines[0],
            lines.remove(lines[0])
            time.sleep(60)
    except IOError:
        print 'No such file in directory'

This prints the first line and then deletes it. When the first value is removed, the list shifts one up making the previous line ( lines[1] ) the new start to the list namely lines[0] .

EDITED:

If you wanted to delete the line from the file as well as from the list of lines you will have to do this:

    import time

    try:
        file = open("childrens-catechism.txt", 'r+')  #open the file for reading and writing
        lines = file.readlines()

        while len(lines) != 0:
            print lines[0],
            lines.remove(lines[0])
            time.sleep(60)

        file.truncate(0) #this truncates the file to 0 bytes
    except IOError:
        print 'No such file in directory'

As far as deleting the lines from the file line for line I am not too sure if that is possible or efficient.