Updating field in attribute table of multiple shapefiles in ArcGIS 10.1

I have almost 100 shapefiles (all having polyline features only) in a single folder with each filename "0","1"…"99" . I need to recalculate the length and another field "slope" which I previously calculated in field calculator:

slope =

math.degrees(math.atan(100/ !Length! ))". 

Now I want to recalculate both fields in each shapefile.
PS: These 100 shapefiles were previously one shapefile whose length and slope has been calculated. But there after I clipped it using features of another shapefile resulting into 100 shapefiles. But the length and slope value was not get upated and it is showing the old values of the single shape file. Now I want to calculate slope and length again for each shapefile which is time consuming so I hope something can be done in a Model Builder or a Python script which could ease my computation.