在python中如何实现：利用matplotlib在世界地图上绘出一些国家，标出这些国家的名字；赋予每个国家不同的数字，国家的颜色随数字变化（colorbar）；要求可以设置画布的大小及分辨率，并给出图例，最终输出图片为PNG格式

要实现这个功能，需要使用以下步骤：

1. 安装 matplotlib 和 basemap 库

pip install matplotlib
pip install basemap

2. 导入库

import matplotlib.pyplot as plt
from mpl_toolkits.basemap import Basemap

3. 创建地图

fig = plt.figure(figsize=(8, 8), dpi=100)
m = Basemap(projection='ortho', resolution=None, lat_0=50, lon_0=-100)

4. 绘制国家

m.fillcontinents(color='#ddaa66', lake_color='#7777ff')
m.drawmapboundary(fill_color='#7777ff')
m.drawcountries(linewidth=0.5, linestyle='solid', color='k', zorder=10)

5. 标注国家名称

for name, lat, lon in zip(country_names, country_lats, country_lons):
    x, y = m(lon, lat)
    plt.text(x, y, name, fontsize=10, color='white', ha='center', va='center')

6. 给每个国家赋予数字，并绘制颜色条

cmap = plt.cm.get_cmap('OrRd')
normalize = plt.Normalize(vmin=min(nums), vmax=max(nums))
colors = [cmap(normalize(num)) for num in nums]
plt.colorbar(mappable=plt.cm.ScalarMappable(norm=normalize, cmap=cmap), label='Population')

7. 保存图片

plt.savefig('world_map.png', bbox_inches='tight')

完整代码如下所示：

import matplotlib.pyplot as plt
from mpl_toolkits.basemap import Basemap

# 假设有一个包含国家名称、经度、纬度和数字的列表
country_names = ['China', 'India', 'USA', 'Indonesia', 'Pakistan']
country_lats = [35.8617, 20.5937, 37.0902, -0.7893, 30.3753]
country_lons = [104.1954, 78.9629, -95.7129, 113.9213, 69.3451]
nums = [1393, 1353, 327, 266, 218]

fig = plt.figure(figsize=(8, 8), dpi=100)
m = Basemap(projection='ortho', resolution=None, lat_0=50, lon_0=-100)

m.fillcontinents(color='#ddaa66', lake_color='#7777ff')
m.drawmapboundary(fill_color='#7777ff')
m.drawcountries(linewidth=0.5, linestyle='solid', color='k', zorder=10)

for name, lat, lon in zip(country_names, country_lats, country_lons):
    x, y = m(lon, lat)
    plt.text(x, y, name, fontsize=10, color='white', ha='center', va='center')

cmap = plt.cm.get_cmap('OrRd')
normalize = plt.Normalize(vmin=min(nums), vmax=max(nums))
colors = [cmap(normalize(num)) for num in nums]
plt.scatter(country_lons, country_lats, latlon=True, c=colors, edgecolor='black', linewidth=1, s=nums, alpha=0.75)

plt.colorbar(mappable=plt.cm.ScalarMappable(norm=normalize, cmap=cmap), label='Population')

plt.title('World Map')
plt.savefig('world_map.png', bbox_inches='tight')
plt.show()