Confused by python file mode "w+"
file, io, python
Solution
Let's say you're opening the file with a `with` statement like you should be. Then you'd do something like this to read from your file:
with open('somefile.txt', 'w+') as f:
# Note that f has now been truncated to 0 bytes, so you'll only
# be able to read data that you write after this point
f.write('somedata\n')
f.seek(0) # Important: return to the top of the file before reading, otherwise you'll just read an empty string
data = f.read() # Returns 'somedata\n'
Note the `f.seek(0)` -- if you forget this, the `f.read()` call will try to read from the end of the file, and will return an empty string.
Problem
From the doc, Modes 'r+', 'w+' and 'a+' open the file for updating (note that 'w+' truncates the file). Append 'b' to the mode to open the file in binary mode, on systems that differentiate between binary and text files; on systems that don’t have this distinction, adding the 'b' has no effect. and here w+ : Opens a file for both writing and reading. Overwrites the existing file if the file exists. If the file does not exist, creates a new file for reading and writing. But, how to read a file open with `w+`?