Question

When executing the following code, after the second read, file gets filled with zero until being 4096 bytes large. I can’t figure out why :

f = open("file.txt", "w+")
f.read()
# gives ''
f.write("Hello")
f.read()
# filled with \x00,\x00
f.close()
# file is 4096 bytes large...

Answer 1

Best way to solve your problem: don’t mix read() and write().

Otherwise: after the write(), use seek() before the second read() to read your file from the beginning:

f = open("file.txt", "w+")
print f.read()      # prints ''
f.write("Hello")
f.seek(0)
print f.read()      # print 'Hello'
f.close()