title: get information from pandas' dataframe and python 3
body: <p>I have two csv files. Contacts and Users. </p>
  
  <p><strong>How I load data into dataframes and merge them</strong></p>
  
  <p>First, I load a dataframe with the name of the users:</p>
  
  <pre><code>import pandas as pd
  import numpy as np
  df_users= pd.read_csv('./Users_001.csv',sep=',',usecols=[0,2,3])
  </code></pre>
  
  <p>Then I load the information from contacts of each user</p>
  
  <pre><code>df_contacts = pd.read_csv('./Contacts_001.csv',sep=',',usecols=[0,1,5,48,55,56,57,83,58])
  </code></pre>
  
  <p>df_users columns name are: <code>user_id, Name, Surname</code></p>
  
  <p>df_contacts columns name are:  <code>Contact ID, id user owner, fullname, qualification, ...</code></p>
  
  <p>I want to merge both dataframes using <code>user_id</code> and <code>'id user owner'</code> since they represent the same information. To to this I first change the name of the columns on <code>df_contacts</code> and then I merge</p>
  
  <pre><code>dfcontactos.columns = ['ID de Contacto','user_id','fullname','qualification','accesibility' ... ]
  df_us_cont = pd.merge(dfcontactos,df_usuarios,on='user_id')
  </code></pre>
  
  <p>Now <code>df_us_cont</code> has the information from users and contacts. </p>
  
  <p><strong>What I want to do</strong></p>
  
  <p>There are only 18 <code>user_id</code> but there are 500 contacts. For each user I want to know:</p>
  
  <ul>
  <li><p>Number of contacts with qualification &lt; 100 </p>
  
  <p>For the contacts that have qualification &lt;100</p>
  
  <p>How many contacts have accesibility >= 4 </p>
  
  <p>Accesibility is a discrete number (0-5))</p></li>
  <li>Number of contacts with qualification > 100 and &lt; 300</li>
  <li>Number of contacts with qualification > 300 </li>
   - 
  </ul>
  
  <p><strong>What I have tried and fail</strong></p>
  
  <pre><code>df_qua_lower100 = df_us_cont[df_us_cont['qualification']&lt;100]
  df_qua_lower100['user_id'].value_counts()
  </code></pre>
  
  <p>So far with this I am able to get the information on how many contacts with <code>qualification&lt;100</code> has each <code>user_id</code>. But I am unable to look how many have '<code>accesibility&gt;=4</code>' </p>
  
  <p>I have tried to explain the best I could</p>