ValueError: xlims must be increasing

ValueError: xlims must be increasing

$ python -c "import matplotlib.pyplot as plt; fig, ax = plt.subplots(); ax.set_xlim(10, 0)"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ValueError: xlims must be increasing

Why this happens

Some scales/backends require increasing limits; reversed order isn’t permitted for certain projections.

Fix

Set limits with lower < upper, or invert using ax.invert_xaxis().

Wrong code

import matplotlib.pyplot as plt
fig, ax = plt.subplots()
ax.set_xlim(10, 0)

Fixed code

import matplotlib.pyplot as plt
fig, ax = plt.subplots()
ax.set_xlim(0, 10)
# Or to reverse direction explicitly:
ax.invert_xaxis()
plt.show()