How to add method to existing class in Python?

Question

I have this really convenient high-level pd.DataFrame saving function that I want to add to pandas. How can I add this method to the pd.DataFrame class?

def to_file(df, path, sep="\t", compression="infer", pickled="infer", verbose=False, **args):
    _ , ext = os.path.splitext(path)
    # Serialization
    if pickled == "infer":
        if ext in {".pkl", ".pgz", ".pbz2"}:
            pickled = True
        else:
            pickled = False
    # Compression
    if compression == "infer":
        if pickled:
            if ext == ".pkl":
                compression = None
            if ext == ".pgz":
                compression = "gzip"
            if ext == ".pbz2":
                compression = "bz2"
        else:
            compression = None
            if path.endswith(".gz"):
                compression = "gzip"
            if path.endswith(".bz2"):
                compression = "bz2"
    if verbose:
        print(
            f"path:\t{path}", 
            f"sep:\t{repr(sep)}",
            f"compression:\t{compression}",
            f"pickled:\t{pickled}", 
            sep="\n", 
            file=sys.stderr,
        )
    if pickled == False:
        df.to_csv(path, sep=sep, compression=compression, **args)
    if pickled == True:
        df.to_pickle(path, compression=compression, **args)

maybe a duplicate of: https://stackoverflow.com/questions/972/adding-a-method-to-an-existing-object-instance — DSLima90, Mar 06 '18 at 20:12

score 5 · Accepted Answer · answered Mar 06 '18 at 20:14

5

Use python class inheritance. This will allow you to use all the methods in a Pandas data frame and still define your own methods.

import pandas as pd

class NewDF(pd.DataFrame)
    def __init__(self, *args):
        pd.DataFrame.__init__(self, *args)

    def to_file(df, path, sep="\t", compression="infer", pickled="infer", verbose=False, **args):
        ...

answered Mar 06 '18 at 20:14

APorter1031

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3

`pd.DataFrame.to_file = to_file` also works but I like the above approach. Thanks, this will come in handy for other things. – O.rka Mar 06 '18 at 20:29

How to add method to existing class in Python?

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