Passing a list of randomForest objects back to R with rpy2 <p>I am trying to combine a number of random forest models using rpy2. The <code>combine</code> command in R looks fairly straight forward but I am not sure how to pass the RF objects from python to R.</p> <p>Simple example:</p> <pre><code>import pandas as pd import numpy as np import sys if sys.version_info[0] &lt; 3: from string import lowercase else: from string import ascii_lowercase as lowercase import rpy2.robjects as robjects from rpy2.robjects import pandas2ri pandas2ri.activate() r = robjects.r r.library("randomForest") df = pd.DataFrame(data=np.random.random(size=(100, 10)), columns=[a for a in lowercase[:10]]) cols = df.columns RF = [] for _ in range(5): df['train'] = np.random.random(size=100) &lt; .75 rf = r.randomForest(robjects.Formula('a~.'), data=df[df.train][cols]) RF.append(rf) </code></pre> <p>When I try and <code>combine</code> RF models in R</p> <pre><code>RFall = r.combine(RF) </code></pre> <p>Returns the error:</p> <pre><code>Error in (function (...) : Argument must be a list of randomForest objects </code></pre> <p>I have looked at other functions in <code>robjects</code> but can't find the one that will do it.</p>