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"# staff\n",
"example of macro to read data from an ascii file and\n",
"create a root file with a Tree.\n",
"\n",
"NOTE: comparing the results of this macro with those of staff.C, you'll\n",
"notice that the resultant file is a couple of bytes smaller, because the\n",
"code below strips all white-spaces, whereas the .C version does not.\n",
"\n",
"\n",
"\n",
"\n",
"**Author:** Wim Lavrijsen \n",
"This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Tuesday, May 19, 2026 at 08:17 PM."
]
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"source": [
"import os\n",
"\n",
"import ROOT\n",
"from ROOT import TFile, TTree, addressof, gROOT"
]
},
{
"cell_type": "markdown",
"id": "84f084cf",
"metadata": {},
"source": [
" A C/C++ structure is required, to allow memory based access"
]
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"0"
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"source": [
"gROOT.ProcessLine(\n",
" \"\"\"struct staff_t {\n",
" Int_t Category;\n",
" UInt_t Flag;\n",
" Int_t Age;\n",
" Int_t Service;\n",
" Int_t Children;\n",
" Int_t Grade;\n",
" Int_t Step;\n",
" Int_t Hrweek;\n",
" Int_t Cost;\n",
" Char_t Division[4];\n",
" Char_t Nation[3];\n",
"};\"\"\"\n",
")"
]
},
{
"cell_type": "markdown",
"id": "273139f1",
"metadata": {},
"source": [
" Function to read in data from ASCII file and fill the ROOT tree"
]
},
{
"cell_type": "code",
"execution_count": 3,
"id": "8e77aacd",
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"outputs": [],
"source": [
"staff = ROOT.staff_t()"
]
},
{
"cell_type": "markdown",
"id": "eb44b18f",
"metadata": {},
"source": [
"The input file cern.dat is a copy of the CERN staff data base\n",
"from 1988"
]
},
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"data": {
"text/plain": [
""
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"source": [
"f = TFile(\"staff.root\", \"RECREATE\")\n",
"tree = TTree(\"T\", \"staff data from ascii file\")\n",
"tree.Branch(\"staff\", staff, \"Category/I:Flag:Age:Service:Children:Grade:Step:Hrweek:Cost\")\n",
"tree.Branch(\"Divisions\", addressof(staff, \"Division\"), \"Division/C\")\n",
"tree.Branch(\"Nation\", addressof(staff, \"Nation\"), \"Nation/C\")"
]
},
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"id": "2835752b",
"metadata": {},
"source": [
"note that the branches Division and Nation cannot be on the first branch"
]
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"name": "stdout",
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"text": [
"******************************************************************************\n",
"*Tree :T : staff data from ascii file *\n",
"*Entries : 3354 : Total = 174374 bytes File Size = 47224 *\n",
"* : : Tree compression factor = 2.91 *\n",
"******************************************************************************\n",
"*Br 0 :staff : Category/I:Flag:Age:Service:Children:Grade:Step:Hrweek:*\n",
"* | Cost *\n",
"*Entries : 3354 : Total Size= 122254 bytes File Size = 28926 *\n",
"*Baskets : 3 : Basket Size= 32000 bytes Compression= 3.32 *\n",
"*............................................................................*\n",
"*Br 1 :Divisions : Division/C *\n",
"*Entries : 3354 : Total Size= 27564 bytes File Size = 8980 *\n",
"*Baskets : 1 : Basket Size= 32000 bytes Compression= 2.38 *\n",
"*............................................................................*\n",
"*Br 2 :Nation : Nation/C *\n",
"*Entries : 3354 : Total Size= 24209 bytes File Size = 9318 *\n",
"*Baskets : 1 : Basket Size= 32000 bytes Compression= 2.19 *\n",
"*............................................................................*\n"
]
}
],
"source": [
"fname = os.path.join(str(ROOT.gROOT.GetTutorialDir()), \"io\", \"tree\", \"cernstaff.dat\")\n",
"with open(fname) as file:\n",
" for line in file.readlines():\n",
" t = line.split()\n",
" staff.Category = int(t[0]) # assign as integers\n",
" staff.Flag = int(t[1])\n",
" staff.Age = int(t[2])\n",
" staff.Service = int(t[3])\n",
" staff.Children = int(t[4])\n",
" staff.Grade = int(t[5])\n",
" staff.Step = int(t[6])\n",
" staff.Hrweek = int(t[7])\n",
" staff.Cost = int(t[8])\n",
" staff.Division = t[9] # assign as strings\n",
" staff.Nation = t[10]\n",
"\n",
" tree.Fill()\n",
"\n",
"tree.Print()\n",
"tree.Write()\n",
"\n",
"f.Close()"
]
}
],
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