[Python] How to give same space for y axis tick labels in Matplotlib for different figures?

I need to plot figures using the same function.

Yaxis tick labels can be 2 digit and sometimes 3 digit integer numbers.

Although I format the y axis tick labels as 3 digit integers, spacing before the left spine slightly changes.

How to give same space for the y axis tick labels so that the left spine of the axis starts at the same location for different figures?

Here is the sample code to replicate these figures:

from matplotlib import pyplot as plt
from matplotlib.ticker import FormatStrFormatter
from matplotlib.ticker import MaxNLocator

import numpy as np
import os

def plot_figure(start, end, figure_name):
fwidth = 15
fheight = 7

fig = plt.figure(figsize=(fwidth, fheight), facecolor=None)
plt.style.use('ggplot')

# define margins
left_margin = 0.95 / fwidth
right_margin = 0.2 / fwidth
bottom_margin = 0.5 / fheight
top_margin = 0.25 / fheight

# create axes
x = left_margin # horiz. position of bottom-left corner
y = bottom_margin # vert. position of bottom-left corner
w = 1 - (left_margin + right_margin) # width of axes
h = 1 - (bottom_margin + top_margin) # height of axes
ax = fig.add_axes([x, y, w, h])

ax.set_facecolor('white')

# This code puts the edge line
for edge_i in ['left', 'bottom','right', 'top']:
ax.spines[edge_i].set_edgecolor("black")
ax.spines[edge_i].set_linewidth(3)

plus_minus = 50
x = np.arange(-plus_minus, plus_minus + 1, 1)
signal_array = np.random.randint(start, end + 1, size = 2*plus_minus+1)
plt.plot(x, signal_array, color='b', label='Signal', linewidth=2, zorder=10)

# This code puts the tick marks
plt.tick_params(axis='both', which='major', labelsize=50, width=3, length=10)
plt.tick_params(axis='both', which='minor', labelsize=50, width=3, length=10)

# This code provides the x and y tick marks and labels
plt.xticks(np.arange(-plus_minus/2, plus_minus/2+1, step=plus_minus/2), fontsize=50)
plt.xlim((-plus_minus, plus_minus))

ax.yaxis.set_major_formatter(FormatStrFormatter('%3d'))
ax.yaxis.set_major_locator(MaxNLocator(integer=True, min_n_ticks=3, nbins=2))
ax.yaxis.set_major_locator(MaxNLocator(3))

figure_file = os.path.join('/Users','burcakotlu','Desktop','test2.png')
fig.savefig(figure_file, dpi=100, bbox_inches="tight")
plt.close(fig)

plot_figure(20, 50, 'test1')
plot_figure(100, 130, 'test2')




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