50 - read readlines and other methods

readlines() method

The readline() method reads a single line from the file.

  • If we want to read multiple lines, we can use a loop.
f = open('myfile.txt', 'r')
while True:
    line = f.readline()
    if not line:
        break
    print(line)

The readlines() method reads all the lines of the file and returns them as a list of strings.

writelines() method

The writelines() method in Python writes a sequence of strings to a file. The sequence can be any iterable object, such as a list or a tuple.

Here's an example of how to use the writelines() method:

f = open('myfile.txt', 'w')
lines = ['line1', 'line2', 'line3']
f.writelines(lines)
f.close()

# output in myfiles.txt:

line1line2line3 # without any spaces
info

if we wanna add space or write strings line by line, we have to add them right in the string.

f = open('myfile.txt', 'w')
lines = ['line1\n', 'line2\n', 'line3\n'] # The \n characters are used to add newline characters to the end of each string.
f.writelines(lines)
f.close()

#output in myfiles.txt
line 1
line 2
line 3

Keep in mind that the writelines() method does not add newline characters between the strings in the sequence.
So this method can't be used for long list or in case of unchangeable lists.

In that case, you can use a loop to write each string separately:

f = open('myfile.txt', 'w')
lines = ['line 1', 'line 2', 'line 3']
for line in lines:
    f.write(line + '\n')
f.close()

It is also a good practice to close the file after you are done with it.

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