arrows_on_line_ignorethis.py

import os
import sys
import logging
import re
import pandas as pd
import numpy as np
import scipy as sp
import csv
import bisect
import uuid
import matplotlib
import colormaps

matplotlib.use('Qt4Agg')
matplotlib.rcParams['backend.qt4'] = 'PySide'
from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.backends.backend_qt4agg import NavigationToolbar2QT as NavigationToolbar
from matplotlib.figure import Figure
from PySide import QtGui, QtCore
from functools import partial
from mat_Zerlegungen import gausselimination
from datetime import datetime
from mpldatacursor import datacursor


def main():
    app = QtGui.QApplication.instance()  # checks if QApplication already exists
    if not app:  # create QApplication if it doesnt exist
        app = QtGui.QApplication(sys.argv)
    # Init
    widg1 = QtGui.QGroupBox(parent=None)
    vertical_layout = QtGui.QVBoxLayout(widg1)
    fig1 = Figure(dpi=72, facecolor=(1, 1, 1),
                  edgecolor=(0, 0, 0))
    canv1 = FigureCanvas(fig1)
    ax1 = fig1.add_subplot(111)
    ax1.set_xlim(-0.06, 0.06)
    ax1.set_ylim(3.35000000e-15, 3.75000000e-15)
    ax1.autoscale(True)
    transform = ax1.transData
    arrow_head = (0.5, 0.15302574986800177)
    arrow_tail = (0.0, 0.30605149973599999)
    arrow_kw = {
        'mutation_scale': 20,
        'color': [
            0.590734,
            0.152563,
            0.40029],
        'linewidth': 1.0,
        'arrowstyle': '->'}
    vertical_layout.addWidget(canv1)
    widg1.show()
    file1 = open('output_1_ignorethis.txt', 'w')
    file1.write(str(transform))
    file1.close()
    print transform
    print 'plotted successfully!'
    p = matplotlib.patches.FancyArrowPatch(
        arrow_tail, arrow_head, transform=transform,
        **arrow_kw)
    ax1.add_patch(p)
    ax1.relim()
    ax1.autoscale_view()
    canv1.draw()
    print 'patch plotted successfully!'
    # Main Loop
    app.exec_()


if __name__ == '__main__':
    main()

Lines 36 and 37 generate an endless loop.
==>> Fixed by adding line 39: ax1.autoscale(True)