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I'm not sure it is good practice to read that many bytes from /dev/urandom. Quoting the Linux man page for /dev/urandom:
 The kernel random-number generator is designed to produce a small amount of
 high-quality seed material to seed a cryptographic pseudo-random number gen‐
 erator (CPRNG). It is designed for security, not speed, and is poorly
 suited to generating large amounts of random data. Users should be very
 economical in the amount of seed material that they read from /dev/urandom
 (and /dev/random); unnecessarily reading large quantities of data from this
 device will have a negative impact on other users of the device.
The (default?) entropy pool size under Linux is 4096 bytes, so reading 2500 bytes will deplete more than half of it, IIUC. Example:
$ cat /proc/sys/kernel/random/poolsize 
4096
$ cat /proc/sys/kernel/random/entropy_avail 
516
$ python -c "import os; os.urandom(300)"
$ cat /proc/sys/kernel/random/entropy_avail 
160