title: Adding a legend to a boxplot in matplotlib/seaborn
body: <p>I am new to Python.</p>
  
  <p>I have generated a boxplot (with a swarmplot overlay) in matplotlib/seaborn using the following code. I would now like to add a legend that follows the color scheme of each box. Many solutions I find online does not seem to apply to this particular type of graph (eg. only work with <a href="https://github.com/mwaskom/seaborn/issues/720" rel="nofollow noreferrer">grouped boxplots</a>).</p>
  
  <p>When I try to implement the code suggested <a href="https://matplotlib.org/1.3.1/users/legend_guide.html" rel="nofollow noreferrer">here</a> I receive the error message.</p>
  
  <p><a href="https://i.stack.imgur.com/atbB0.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/atbB0.jpg" alt="enter image description here"></a></p>
  
  <p>All input is greatly appreciated!</p>
  
  <pre><code># Import libraries and modules
  
  import pandas as pd
  import numpy as np
  import matplotlib.pyplot as plt
  import seaborn as sns
  
  # Set seaborn style.
  
  sns.set(style="whitegrid", palette="colorblind")
  
  # Load summary tidy data.
  
  tidy = pd.read_csv('tidy.csv')
  
  # Define plots for tidy data
  
  fig, ax = plt.subplots(figsize=(10,6))
  ax = sns.boxplot(x='header1', y='header2', data=tidy, order=["header1", "header2"])
  ax = sns.swarmplot(x="header1", y="header2", data=tidy, color=".25", order=["header1", "header2"])
  labels = [item.get_text() for item in ax.get_xticklabels()]
  labels[0] = 'header1'
  labels[1] = 'header2'
  ax.set_xticklabels(labels)
  ax.legend(loc='best')
  </code></pre>
  
  <p>Example of the data I am working with.</p>
  
  <pre><code>Object,Metric,Length
  MT1,B2A1,3.57675
  MT1,B2A2,2.9474600000000004
  MT1,B2A3,2.247772857142857
  MT1,B2A4,3.754455
  MT1,B2A5,2.716282
  MT1,B2A6,2.91325
  MT10,B2A1,3.34361
  MT10,B2A2,2.889958333333333
  MT10,B2A3,2.22087
  MT10,B2A4,2.87669
  MT10,B2A5,1.6745005555555557
  MT12,B2A1,3.3938900000000003
  MT12,B2A2,2.00601
  MT12,B2A3,2.1720200000000003
  MT12,B2A4,2.452923333333333
  </code></pre>