[] is false in Python; so are other empty aggregates like () and {}; collection types implemented in Python typically follow the same pattern. Thus: >>> if (

[] is false in Python; so are other empty aggregates like () and {}; collection types implemented in Python typically follow the same pattern. Thus: >>> if (): print "tuple" >>> if []: print "list" >>> if {}: print "dict" >>> if set(): print "set" >>> if "": print "string" >>> import collections >>> if collections.Counter(): print "counter" >>> if collections.deque(): print "deque" >>> (Observe that none of these prints anything.)