Pandas dataframe column selection

Question

I am using Pandas to select columns from a dataframe, olddf. Let's say the variable names are 'a', 'b','c', 'starswith1', 'startswith2', 'startswith3',...,'startswith10'.

My approach was to create a list of all variables with a common starting value.

    filter_col = [col for col in list(health) if col.startswith('startswith')]

I'd like to then select columns within that list as well as others, by name, so I don't have to type them all out. However, this doesn't work:

newdf = olddf['a','b',filter_col]

And this doesn't either:

newdf = olddf[['a','b'],filter_col]

I'm a newbie so this is probably pretty simple. Is the reason this doesn't work because I'm mixing a list improperly?

Thanks.

unutbu · Accepted Answer · 2016-04-08 00:33:23Z

2

Use

newdf = olddf[['a','b']+filter_col]

since adding lists concatenates them:

In [264]: ['a', 'b'] + ['startswith1']
Out[264]: ['a', 'b', 'startswith1']

Alternatively, you could use the filter method:

newdf = olddf.filter(regex=r'^(startswith|[ab])')

answered Apr 8, 2016 at 0:33

unutbu

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