how to set range of y axis in matplotlib code example

Example 1: ylim python

plt.ylim([a,b])

Example 2: how to set axis range matplotlib

# For a given y=time-dependent variable, x=time
fig, ax = plt.subplots(figsize=(12, 6))

ax.plot(y, label='y')
#'lower' is lower limit of the range you wanna set
#'upper' is upper limit of the range you wanna set
plt.xlim(lower, upper)