I have read about dataframe loc. I could not understand why the length of dataframe(indexPD) is being supplied to loc as a first argument. Basically what does this loc indicate? Answer That is simply telling pandas you want to do the operation on all of the rows of that column of your dataframe. Consider this…
Tag: python
Speeding-up pandas column operation based on several rules
I have a data frame consisting of 5.1 mio rows. Now, consider only a query of my data frame which has the following form: date ID1 ID2 201908 a X 201905 b Y 201811 a Y 201807 a Z You can assume that the date is sorted and that there are no duplicates in the subset [‘ID1’, ‘ID2’]. Now, …
How to add PostGIS SQL SELECT query as layer to QGIS 3 project using Python console?
I want to add a PostGIS SELECT query as a new layer to a QGIS 3 project using the Python console. It is a simple process to do this using the SQL Window in the DB Manager of QGIS. Here you can create a layer from any SQL query of a PostGIS enabled PostgreSQL database. The following works for adding
Pandas filter without ~ and not in operator
I have two dataframes like as below I would like to do the below a) Check whether the ID and Name from df1 is present in df2. b) If present in df2, put Yes in Status column or No in Status column. Don’t use ~ or not in operator because my df2 has million of rows. So, it will result
How to store CSV file in database?
There is a output file from Python Pandas with a lot of columns with headers. I need to be able handle this file by script and get CSV files in different columns positions. For example, initial file has columns As variation I need to get it in different sequence: I wonder what is the best way to store this fi…
Exponential fit in pandas
I have this data: The data seems to follow an exponential curve. Let’s see the plot: I want to fit an exponential curve ($$ y = Ae^{Bx} $$, A times e to the B*X)and add it as a column in Pandas. Firstly I tried to log the values: And then to use Numpy to fit the equation: But I get
Appending an empty list to a numpy array changes its dtype
I have a numpy array of integers. In my code I need to append some other integers from a list, which works fine and gives me back an array of dtype int64 as expected. But it may happen that the list of integers to append is empty. In that case, numpy returns an array of float64 values. Exemplary code below:
Identify the columns which contain zero and output its location
Suppose I have a dataframe where some columns contain a zero value as one of their elements (or potentially more than one zero). I don’t specifically want to retrieve these columns or discard them (I know how to do that) – I just want to locate these. For instance: if there is are zeros somewhere …
Django celery error while adding tasks to RabbitMQ message queue : AttributeError: ‘ChannelPromise’ object has no attribute ‘__value__’
I have setup celery, rabbitmq and django web server on digitalocean. RabbitMQ runs on another server where my Django app is not running. When I am trying to add the tasks to the queue using delay I am getting an error AttributeError: ‘ChannelPromise’ object has no attribute ‘value’ Fro…
How to print exception errors and trace tacks in a file when there’s an error in my code?
I want that whenever an error is raised in my code, traceback.print_exception() execute so I can have any errors in a file to check… Is it possible somehow? Answer You could try wrapping your code in a try/except block, and call the function in the except. It might look like this: