Pandas: add a column if it does not exist

Question

I am new to using pandas and writing a script where I read in a data framework and then do some calculations on some columns.

Sometimes I will have a “Met” column:

df = pd.read_csv(File, sep='\t', compression='gzip', header=0, names=["Chrom", "Site", "coverage", "Met"]) 

In other cases, I will have:

 df = pd.read_csv(File, sep='\t', compression='gzip', header=0, names=["Chrom", "Site", "coverage", "freqC"]) 

I need to do some calculations with the “Met” column, so if it is missing, I will need to calculate it using:

 df['Met'] = df['freqC'] * df['coverage'] 

Is there a way to check if the "Met" column is present in the data frame, and if not add it?

Answer 1

You check it as follows:

 if 'Met' not in df: df['Met'] = df['freqC'] * df['coverage']