Python: Why does it say that my file is not open to read it?

Question

It says that my file is not open to read the file entered, but it is because target = open(textname) What's wrong?

from sys import argv
filename, textname = argv
target = open(textname, "w")
print "Do you want to truncate %r?" % textname
raw_input("PRESS RETURN KEY IF YES")
target.truncate()
print "What would you like to type now?"
line1 = raw_input("Line 1--> ")
target.write(line1)
target.write("\n")
line2 = raw_input("Line 2--> ")
target.write(line2)
target.write("\n")
line3 = raw_input ("Line 3--> ")
target.write(line3)
target.write("\n")
print target.read()

THANK YOU!

Opening the file in "w" mode automatically truncates it. Maybe you want "r+" mode instead? — Hugh Bothwell, Feb 26 '15 at 02:47

score 4 · Accepted Answer · edited May 23 '17 at 11:52

First change the file open mode to r+(or w+), and then add one line target.seek(0,0) before you try to print the content.

from sys import argv
filename, textname = argv
target = open(textname, "r+")
print "Do you want to truncate %r?" % textname
raw_input("PRESS RETURN KEY IF YES")
target.truncate()
print "What would you like to type now?"
line1 = raw_input("Line 1--> ")
target.write(line1)
target.write("\n")
line2 = raw_input("Line 2--> ")
target.write(line2)
target.write("\n")
line3 = raw_input ("Line 3--> ")
target.write(line3)
target.write("\n")
target.seek(0,0)
print target.read()

You can check the seek method in another answer in Stackoverflow for more information.

score 2 · Answer 2 · answered Feb 26 '15 at 02:47

target = open(textname, "w")
:
print target.read()

What do you think it should do when you've told it to open the file as write-only?

If you want to be able to both read and write, use the r+ mode (you can also use w+ but that will truncate the file regardless).

score 2 · Answer 3 · edited May 23 '17 at 10:27

2

I think the best way would be two first open file for writing, and then when you are done with it, open for reading. For me personally, its not very natural for a file to be open for writing and reading at the same time. Usually I tend to have the file either open for writing or reading. Here you can find more info how to read and write files the same time.

from sys import argv

filename, textname = argv

print "Do you want to truncate %r?" % textname
raw_input("PRESS RETURN KEY IF YES")
print "What would you like to type now?"

with open(textname, "w") as target:
    line1 = raw_input("Line 1--> ")
    target.write(line1)
    target.write("\n")
    line2 = raw_input("Line 2--> ")
    target.write(line2)
    target.write("\n")
    line3 = raw_input ("Line 3--> ")
    target.write(line3)
    target.write("\n")

with open(textname, "r") as target:
    print target.read()

edited May 23 '17 at 10:27

Community

1
1

answered Feb 26 '15 at 02:49

Marcin

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"Its not very natural for a file to be open for writing and reading at the same time" - I find that a truly bizarre contention :-) – paxdiablo Feb 26 '15 at 02:50
@paxdiablo Maybe its my only way of working with files in python . I will change the sentence. – Marcin Feb 26 '15 at 02:53
@Marcin I work with files the same way. I never use `'r+'` mode, always write to the file, then read from the file. – Adam Smith Feb 26 '15 at 02:55

Python: Why does it say that my file is not open to read it?

3 Answers3