Re: checking, if a file exists

*To*: mathgroup at smc.vnet.net*Subject*: [mg84403] Re: checking, if a file exists*From*: David Reiss <dbreiss at gmail.com>*Date*: Fri, 21 Dec 2007 03:25:31 -0500 (EST)*References*: <fkeo2q$2fc$1@smc.vnet.net>

You want to use === rather than ==. Hope this helps... --David On Dec 20, 4:50=A0pm, vejra... at icpf.cas.cz wrote: > Hello, > > I am new to Mathematica & I have the following problem: I need to > 1. check, if a file ("data.dat") with some computationally intensive > results exists > 2. if yes, read the file > 3. if no, do the calculation > > I have written (in Mathematica 6) the following: > > =A0 fileName = "...some path ... \\data.dat"; > =A0 data = If[FileType[fileName] == File, Import[fileName], > calculate[0]] > > It reads correctly the data if the file exists. But if the file does > not exists, it returns > > =A0 If[None == File, Import[fileName], calculate[0]] > > Evidently, the problem is, that > > =A0 FileType[fileName] == File > > returns correctly True if the file exists, but it does not return > False when the file is missing -- it returns only None == File. > > How to do that? > > Thank you. > > Jiri