Random No Generator

Question

My concern is written below:

Why does this code return this error?

import random
with open('rn.txt', 'w') as f:
    for i in range(10):
        number = random.random()
        f.write(str(number) + '\n')
        content=f.read()
print (content)

Error:

Traceback (most recent call last)
<ipython-input-11-ddb88b6f5426> in <module>
      4         number = random.random()
      5         f.write(str(number) + '\n')
----> 6         content=f.read()
      7 print (content)

UnsupportedOperation: not readable

Why does this code write only a single value to the file?

import random
for i in range(10):
    with open('rn.txt', 'w') as f:
        number = random.random()
        f.write(str(number) + '\n')
        content=f.read()
        print (content)

This code is supposed to generate 10 random numbers and write them to the file rn.txt. What am I doing wrong?

In your first code you try to read from a file you open for writing. In the second code you recreate the file during every run of the loop. — Matthias, Aug 16 '21 at 16:15
Your indentation is confusing. As it stands, that's not executable. But I'm also unsure about what you're trying to achieve. Anyway, this may help you to get started:- https://stackoverflow.com/questions/6648493/how-to-open-a-file-for-both-reading-and-writing — , Aug 16 '21 at 16:33
@Sujay If one wants to write it like that the file should be opend in append-mode. But opening the file before the loop is a better idea. And of course reading the file makes no sense. — Matthias, Aug 16 '21 at 16:45
Both of these result in the same error. You cannot read from a file that you have explicitly opened only for writing. — MisterMiyagi, Aug 17 '21 at 10:04
Have a look at this image to better understand the different file opening modes https://stackoverflow.com/a/30566011/1362735 — heretolearn, Aug 17 '21 at 10:05

score 0 · Answer 1 · answered Aug 17 '21 at 09:55

You're trying to perform both read and write operations to a file which is opened in read or write mode. Choose one at a time.

For example, the following could work:

import random

# first open the file in Write mode ('w')
with open('rn.txt', 'w') as f:
    for i in range(10):
        f.write(str(random.random()) + '\n')

# now open the file in Read mode ('r')
with open('rn.txt', 'r') as f:
    for line in f:
        print(line)

Random No Generator

1 Answers1