Code import pandas as pd import numpy as np df = pd.DataFrame({"K1":[1,2,3],"K2":[4,5,6]}) df["result"] = (df["K1"].shift(1)*df["K2"]).fillna(1)[::-1] #line A print(df["result"]) print((df["K1"].shift(1)*df["K2"]).fillna(1)[::-1]) #line B print((df["K1"].shift(1)*df["K2"]).fillna(1)) # line C Output 0 1.0 1 5.0 2 12.0 Name: result, dtype: float64 2 12.0 1 5.0 0 1.0 dtype: float64 0 1.0 1 5.0 2 12.0 dtype: float64 Why column result … Read more
I need a good explanation (references are a plus) on Python slicing.
Python docs says that slicing a list returns a new list.
Now if a “new” list is being returned I’ve the following questions related to “Assignment to slices”
What are the most common pandas ways to select/filter rows of a dataframe whose index is a MultiIndex?
This Python code:
I have the following problem.
I see at many places the use of slice assignment for lists. I am able to understand its use when used with (non-default) indices, but I am not able to understand its use like:
I load some machine learning data from a CSV file. The first 2 columns are observations and the remaining columns are features.
I am trying to implement slice functionality for a class I am making that creates a vector representation.
I have a large dataframe (>3MM rows) that I’m trying to pass through a function (the one below is largely simplified), and I keep getting a Memory Error message.