Question: How do you write data to an already existing file at the beginning of the file with out writing over what’s already there and with out reading the entire file into memory? (e.g. prepend)
Info:
I’m working on a project right now where the program frequently dumps data into a file. this file will very quickly balloon up to 3-4gb. I’m running this simulation on a computer with only 768mb of ram. pulling all that data to the ram over and over will be a great pain and a huge waste of time. The simulation already takes long enough to run as it is.
The file is structured such that the number of dumps it makes is listed at the beginning with just a simple value, like 6. each time the program makes a new dump I want that to be incremented, so now it’s 7. the problem lies with the 10th, 100th, 1000th, and so dump. the program will enter the 10 just fine, but remove the first letter of the next line:
“9\n580,2995,2083,028\n…”
“10\n80,2995,2083,028\n…”
obviously, the difference between 580 and 80 in this case is significant. I can’t lose these values. so i need a way to add a little space in there so that I can add in this new data without losing my data or having to pull the entire file up and then rewrite it.
Basically what I’m looking for is a kind of prepend function. something to add data to the beginning of a file instead of the end.
Programmed in Python
~n
It’s not addressing your original question, but here are some possible workarounds:
The first couple of options are a little more work up front, but provide more flexibility. The last option is the easiest solution to your current problem.