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copied!<blockquote> <ul> <li>Are variables in a memory buffer, or are variable values written to disk?</li> </ul> </blockquote> <p>Variables are in a memory buffer. You can see this (on Linux) by running (if you only have one running python process)</p> <pre><code>pidof python | awk '{print "lsof -a -p "$1}' | bash </code></pre> <p>Sample output:</p> <pre><code>COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME python 19858 jazzpi cwd DIR 8,1 12288 135854 /home/jazzpi python 19858 jazzpi rtd DIR 8,1 4096 2 / python 19858 jazzpi txt REG 8,1 2728836 532918 /usr/bin/python2.7 python 19858 jazzpi mem REG 8,1 125424 57 /lib/i386-linux-gnu/libtinfo.so.5.9 python 19858 jazzpi mem REG 8,1 247008 237 /lib/i386-linux-gnu/libreadline.so.6.2 python 19858 jazzpi mem REG 8,1 21648 131133 /usr/lib/python2.7/lib-dynload/readline.so python 19858 jazzpi mem REG 8,1 2965552 530650 /usr/lib/locale/locale-archive python 19858 jazzpi mem REG 8,1 114788 13 /lib/i386-linux-gnu/libgcc_s.so.1 python 19858 jazzpi mem REG 8,1 1437864 4337 /lib/i386-linux-gnu/i686/cmov/libc-2.13.so python 19858 jazzpi mem REG 8,1 148996 4334 /lib/i386-linux-gnu/i686/cmov/libm-2.13.so python 19858 jazzpi mem REG 8,1 95896 129 /lib/i386-linux-gnu/libz.so.1.2.7 python 19858 jazzpi mem REG 8,1 9800 4326 /lib/i386-linux-gnu/i686/cmov/libutil-2.13.so python 19858 jazzpi mem REG 8,1 9844 4330 /lib/i386-linux-gnu/i686/cmov/libdl-2.13.so python 19858 jazzpi mem REG 8,1 117009 4327 /lib/i386-linux-gnu/i686/cmov/libpthread-2.13.so python 19858 jazzpi mem REG 8,1 26064 523330 /usr/lib/i386-linux-gnu/gconv/gconv-modules.cache python 19858 jazzpi mem REG 8,1 117960 35 /lib/i386-linux-gnu/ld-2.13.so python 19858 jazzpi 0u CHR 136,3 0t0 6 /dev/pts/3 python 19858 jazzpi 1u CHR 136,3 0t0 6 /dev/pts/3 python 19858 jazzpi 2u CHR 136,3 0t0 6 /dev/pts/3 </code></pre> <p>You can see it doesn't open any files to write to them. Also, from StackOverflow description of tag <code>variable</code>:</p> <blockquote> <p>A variable is a named data storage location <strong>in memory.</strong></p> </blockquote> <p>However, when your computer is running out of memory, it can write contents of the RAM to the disk (i. e. pagefile.sys on Windows, swap partition on Linux). This also usually happens when you send your OS into Hibernate mode.</p> <blockquote> <ul> <li>Is it risky to do this if the output is VERY large?</li> </ul> </blockquote> <p>Writing to swap is a last resort of your OS and is something you should try to avoid, since reading from disk is a LOT slower than reading from RAM (also see <a href="http://norvig.com/21-days.html#Answers" rel="nofollow noreferrer">Teach yourself programming in 10 years</a>).</p> <blockquote> <ul> <li>What are safer alternatives?</li> </ul> </blockquote> <p>So if you're dealing with huge outputs that are big enough to possibly overflow your PC's RAM, you should consider dumping that data to a temporary file on your disk periodically (e. g. every 10MB or so), if possible.</p> <p>If you want to read from an output stream, I'd also recommend you have a look at <a href="https://stackoverflow.com/questions/375427/non-blocking-read-on-a-subprocess-pipe-in-python/4896288#4896288">this</a>.</p>

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