You could do this in a few lines with shapely and GeoPandas (which uses Fiona under the hood for file i/o). You can use shapely.geometry.box to create the rectangles, convert it to a GeoDataFrame, and use the to_file method to save as a shapefile:

from pandas import DataFrame
from geopandas import GeoDataFrame
from shapely.geometry import box

data = DataFrame.from_csv('rect.csv')
boxes = [box(row[1]['xl'], row[1]['yb'], row[1]['xr'], row[1]['yt'])
         for row in data.iterrows()]
df = GeoDataFrame(boxes, columns=['geometry'], index=data.index)
df.to_file('out.shp', driver='ESRI Shapefile')

You could do this in a few lines with shapely and GeoPandas (which uses Fiona under the hood for file i/o). You can use shapely.geometry.box to create the rectangles, convert it to a GeoDataFrame, and use the to_file method to save as a shapefile:

from pandas import DataFrame
from geopandas import GeoDataFrame
from shapely.geometry import box

data = DataFrame.from_csv('rect.csv')
boxes = [box(row['xl'], row['yb'], row['xr'], row['yt'])
         for key, row in data.iterrows()]
df = GeoDataFrame(boxes, columns=['geometry'], index=data.index)
df.to_file('out.shp', driver='ESRI Shapefile')