I'm trying to use an if to verify if a value in a dataframe equals a certain value i got before. Here's an extract of the dataframe:

    usager     heures demandes heure arrivée ascenseur heures arrivée étage  \
0   1181.0 2019-04-27 07:00:27     2019-04-27 07:00:27  2019-04-27 07:00:43   
1   1181.0 2019-04-27 12:11:54     2019-04-27 12:12:10  2019-04-27 12:12:26   
2   1181.0 2019-04-27 12:55:52     2019-04-27 12:56:06  2019-04-27 12:56:22   
3   1181.0 2019-04-27 17:25:49     2019-04-27 17:26:05  2019-04-27 17:26:21   
0    826.0 2019-04-27 07:00:50     2019-04-27 07:00:50  2019-04-27 07:00:59   
..     ...                 ...                     ...                  ...   
3    677.0 2019-04-27 17:38:47     2019-04-27 17:39:17  2019-04-27 17:39:34   
0    667.0 2019-04-27 09:59:38     2019-04-27 09:59:54  2019-04-27 10:00:09   
1    667.0 2019-04-27 12:23:24     2019-04-27 12:23:39  2019-04-27 12:23:54   
2    667.0 2019-04-27 13:25:16     2019-04-27 13:25:28  2019-04-27 13:25:43   
3    667.0 2019-04-27 18:01:03     2019-04-27 18:01:18  2019-04-27 18:01:33   

   mode transport  etage_demandes  attente  temps dans ascenseur  anomalie  
0       Ascenseur            33.0      0.0                  16.0     False  
1       Ascenseur             0.0     16.0                  16.0     False  
2       Ascenseur            33.0     14.0                  16.0     False  
3       Ascenseur             0.0     16.0                  16.0     False  
0       Ascenseur            18.0      0.0                   9.0     False  
..            ...             ...      ...                   ...       ...  
3       Ascenseur             0.0     30.0                  17.0     False  
0       Ascenseur            30.0     16.0                  15.0     False  
1       Ascenseur             0.0     15.0                  15.0     False  
2       Ascenseur            30.0     12.0                  15.0     False  
3       Ascenseur             0.0     15.0                  15.0     False  

With 'usager' being an unique id for each person, i'm trying to find the level where each person works which is shown in etage_demandes when it's not null. Each row in the dataframe is a movement from a level to another and each person moves 4 times.

Because of how the dataframe is made I tried to do this:

memory=0
print(df['usager'][1:2])
etage_travail=[df[:0]['etage_demandes']]
for i in range (4,len(df['usager'])):
    if (df['usager'][i-1:i]=!memory):
        memory=df['usager'][i-1:i]
        for i in range (0,4):
            etage_travail.append(df[i-1:i]["etage_demandes"])
        

Where I go through each row and get the work level for each person when the id is not the same as the id of the row before. but I can't seem to write the condition in a way so that it works.