pythonmap和reduce的用法
1人问答
问题描述：
pythonmap和reduce的用法
饶伏波回答：
map(function,sequence[,sequence,...])->list
Returnalistoftheresultsofapplyingthefunctiontotheitemsof
theargumentsequence(s).Ifmorethanonesequenceisgiven,the
functioniscalledwithanargumentlistconsistingofthecorresponding
itemofeachsequence,substitutingNoneformissingvalueswhennotall
sequenceshavethesamelength.IfthefunctionisNone,returnalistof
theitemsofthesequence(oralistoftuplesifmorethanonesequence).
reduce(...)
reduce(function,sequence[,initial])->value
Applyafunctionoftwoargumentscumulativelytotheitemsofasequence,
fromlefttoright,soastoreducethesequencetoasinglevalue.
Forexample,reduce(lambdax,y:x+y,[1,2,3,4,5])calculates
((((1+2)+3)+4)+5).Ifinitialispresent,itisplacedbeforetheitems
ofthesequenceinthecalculation,andservesasadefaultwhenthe
sequenceisempty.
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