python - Why memory usage keep growing when I repeatedly open and close the same file -

here code:

while true:     open('a', 'w'):         assert true # sth 

when run it, system total memory usage kept growing. 4 core cpu goes 100%.

why happening?

shouldn't linux kernel close fds , free memory ?

my environment:

• ubuntu 14.04 kernel: x86_64 linux 3.13.0-77-generic
• python 2.7.6
• cpu: intel core i3-2350m cpu @ 2.3ghz
• ram: 7878mib

now can't reproduce problem running original code:

def main():     key_list = ""     in xrange(10000000, 1000000000):         key_list = key_list + str(i) + "\n"         if len(key_list) > 10000:             open("./passwd1.txt", "a+") f:                 f.write(key_list)             # del key_list             key_list = ""             print "done" 

weird...