如何在matplotlib中使用空格将轴号格式设置为千位？

import matplotlib.pyplot as plt
import matplotlib.ticker as ticker

fig, ax = plt.subplots()

def format_thousands(x, pos):
    """自定义千位格式化函数"""
    return '{:,.0f}'.format(x).replace(',', ' ')

ax.xaxis.set_major_formatter(ticker.FuncFormatter(format_thousands))
ax.yaxis.set_major_formatter(ticker.FuncFormatter(format_thousands))

plt.plot([1000, 2000, 3000, 4000], [1000, 4000, 2000, 3000])
plt.show()