Whenever I plot, the X axis sorts automatically (for example, if i enter values 3, 2, 4, it will automatically sort the X axis from smaller to larger.
How can I do
You could provide a dummy x-range, and then override the xtick labels. I do agree with the comments above questioning wether its the best solution, but thats hard to judge without any context.
If you really want to, this might be an option:
fig, ax = plt.subplots(1,2, figsize=(10,4))
x = [2,4,3,6,1,7]
y = [1,2,3,4,5,6]
ax[0].plot(x, y)
ax[1].plot(np.arange(len(x)), y)
ax[1].set_xticklabels(x)

edit: If you work with dates, why not plot the real date on the axis (and perhaps format it by the day-of-month if you do want 29 30 1 2 etc on the axis?