How do I join the values of two DataFrame columns as one

Question

I have a dataframe data with these columns col1 and col1.1 .

data:
ID     Col1    Col1.1
1      21      Water, Salt
13     18      Onions
101    30      Replaceable with oil, water, acid

I want data to be:

data:
ID     Col1
1      21: Water, Salt 
13     18: Onions
101    30: Replaceable with oil, water, acid

So far, I have:

data['Col'] = ': '.join(str(list(zip(data['Col1'], data['Col1.1']))).split("', ")).replace("'", "").replace("(", "").replace(")", "").replace("[", "").replace("]", "")

NOTE: I get a SettingWithCopyWarning on running this.

How do I go about this? Thank you all

Answer 1

Use str.cat :

df['Col1'].astype(str).str.cat(df['Col1.1'], sep=': ')
Out: 
0                          21: Water, Salt
1                               18: Onions
2    30: Replaceable with oil, water, acid

You need to assign this back and drop the other column to get exactly the same output:

df['Col1'] = df['Col1'].astype(str).str.cat(df['Col1.1'], sep=': ')
df = df.drop('Col1.1', axis=1)

Or, all in one line, thanks to MaxU :

df['Col1'] = df['Col1'].astype(str).str.cat(df.pop('Col1.1'), sep=': ')