Frequency and Phase Response of Oscillators

from pylab import *
from scipy import optimize 
import csv
import time 
def sineFunc(x, a1, a2, a3, a4):
	return a4 + a1*sin(abs(a2*(2*pi))*x + a3)

with open('mycsv.csv', 'r') as csv_file:
	csv_reader = csv.DictReader(csv_file)
	with open('set1.1.csv','w') as new_file:
		fieldnames = ['freq','gain','phase']
		csv_writer =csv.DictWriter(new_file,fieldnames =fieldnames ,delimiter=',')
		csv_writer.writeheader()
		f = 1500 
		while f < 5000: 
			if f == 4000:
				break
			f += 10
			p.set_sine(f)
			time.sleep(0.1)
			t,v, tt,vv = p.capture2(1000, 20)   # captures A1 and A2
			f1 = [1, f, 0.0, 0.0]   # Amp, freq, phase , offset
			f1, pcov = optimize.curve_fit(sineFunc, t*0.001, v, f1)
			f2 = [1, f, 0.0, 0.0]   # Amp, freq, phase , offset
			f2, pcov = optimize.curve_fit(sineFunc, tt*0.001, vv, f2)
			gain = abs(f1[0]/f2[0])
			dphi = (f2[2] - f1[2]) * 180/ pi
			csv_writer.writerow({'freq':f, 'gain':gain, 'phase':dphi})