[tutorials] Fixup staff.py tutorial

 * Format code
 * Fix linter warnings
 * Close TFile explicitly (avoiding also an unused variable warning)
 * Close `.dat` file correctly using `with` statement
 * Replace invalid regular expression with just `split()`, which already
   splits on whitespaces already

Author: guitargeek

tutorials/io/tree/staff.py

@@ -12,25 +12,28 @@
 ##
 ## \author Wim Lavrijsen
 
-import re, array, os
+import os
+
 import ROOT
-from ROOT import TFile, TTree, gROOT, addressof
+from ROOT import TFile, TTree, addressof, gROOT
 
 ## A C/C++ structure is required, to allow memory based access
 gROOT.ProcessLine(
-"struct staff_t {\
-   Int_t           Category;\
-   UInt_t          Flag;\
-   Int_t           Age;\
-   Int_t           Service;\
-   Int_t           Children;\
-   Int_t           Grade;\
-   Int_t           Step;\
-   Int_t           Hrweek;\
-   Int_t           Cost;\
-   Char_t          Division[4];\
-   Char_t          Nation[3];\
-};" );
+    """struct staff_t {
+   Int_t           Category;
+   UInt_t          Flag;
+   Int_t           Age;
+   Int_t           Service;
+   Int_t           Children;
+   Int_t           Grade;
+   Int_t           Step;
+   Int_t           Hrweek;
+   Int_t           Cost;
+   Char_t          Division[4];
+   Char_t          Nation[3];
+};"""
+)
+
 
 ## Function to read in data from ASCII file and fill the ROOT tree
 def staff():
@@ -40,33 +43,37 @@ def staff():
     # The input file cern.dat is a copy of the CERN staff data base
     # from 1988
 
-    f = TFile( 'staff.root', 'RECREATE' )
-    tree = TTree( 'T', 'staff data from ascii file' )
-    tree.Branch( 'staff', staff, 'Category/I:Flag:Age:Service:Children:Grade:Step:Hrweek:Cost' )
-    tree.Branch( 'Divisions', addressof( staff, 'Division' ), 'Division/C' )
-    tree.Branch( 'Nation', addressof( staff, 'Nation' ), 'Nation/C' )
+    f = TFile("staff.root", "RECREATE")
+    tree = TTree("T", "staff data from ascii file")
+    tree.Branch("staff", staff, "Category/I:Flag:Age:Service:Children:Grade:Step:Hrweek:Cost")
+    tree.Branch("Divisions", addressof(staff, "Division"), "Division/C")
+    tree.Branch("Nation", addressof(staff, "Nation"), "Nation/C")
 
     # note that the branches Division and Nation cannot be on the first branch
-    fname = os.path.join(str(ROOT.gROOT.GetTutorialDir()), 'io', 'tree', 'cernstaff.dat')
-    for line in open(fname).readlines():
-        t = list(filter( lambda x: x, re.split( '\s+', line ) ) )
-        staff.Category = int(t[0])             # assign as integers
-        staff.Flag     = int(t[1])
-        staff.Age      = int(t[2])
-        staff.Service  = int(t[3])
-        staff.Children = int(t[4])
-        staff.Grade    = int(t[5])
-        staff.Step     = int(t[6])
-        staff.Hrweek   = int(t[7])
-        staff.Cost     = int(t[8])
-        staff.Division = t[9]                  # assign as strings
-        staff.Nation   = t[10]
+    fname = os.path.join(str(ROOT.gROOT.GetTutorialDir()), "io", "tree", "cernstaff.dat")
+    with open(fname) as file:
+        for line in file.readlines():
+            t = line.split()
+            staff.Category = int(t[0])  # assign as integers
+            staff.Flag = int(t[1])
+            staff.Age = int(t[2])
+            staff.Service = int(t[3])
+            staff.Children = int(t[4])
+            staff.Grade = int(t[5])
+            staff.Step = int(t[6])
+            staff.Hrweek = int(t[7])
+            staff.Cost = int(t[8])
+            staff.Division = t[9]  # assign as strings
+            staff.Nation = t[10]
 
-        tree.Fill()
+            tree.Fill()
 
     tree.Print()
     tree.Write()
 
+    f.Close()
+
+
 #### run fill function if invoked on CLI
-if __name__ == '__main__':
-   staff()
+if __name__ == "__main__":
+    staff()