write a root file

import ROOT
import array
outfile = ROOT.TFile(outfilename,"RECREATE") # Erases any existing file.
# Create a one-element python array to hold the value (could also use numpy).
time_arr = array.array("d" ,[0])
binomial_arr = array.array("l",[0]) # And so on for every variable...
# Create the tree and the branch manually.
t = ROOT.TTree(treename ,"tree title")
t.Branch("time", time_arr , "time/D") 
t.Branch("binomial", binomial_arr, "binomial/L") 
# D for doubles 
# L for integers
# Now loop over the file manually:
with open(infilename ,"r") as csvfile: 
    reader = csv.reader(csvfile)
    for row in reader:
        if row[0].startswith("#"): # skip comment lines continue
        time_arr[0] = float(row[0]) # Important: change the CONTENT of the arrays. 
        binomial_arr[0] = int(row[1])
        t.Fill()
# Write the data from the TFile to the actual file on disk.
outfile.Write() 
outfile.Close()