How do I split a string into several columns in a dataframe with pandas Python?

The str.split method has an expand argument:

>>> df['string'].str.split(',', expand=True)
         0        1         2
0  astring      isa    string
1  another   string        la
2      123      232   another
>>>

With column names:

>>> df['string'].str.split(',', expand=True).rename(columns = lambda x: "string"+str(x+1))
   string1  string2   string3
0  astring      isa    string
1  another   string        la
2      123      232   another

Much neater with Python >= 3.6 f-strings:

>>> (df['string'].str.split(',', expand=True)
...              .rename(columns=lambda x: f"string_{x+1}"))
  string_1 string_2  string_3
0  astring      isa    string
1  another   string        la
2      123      232   another