You can use pyarrow.compute.binary_join_element_wise to join a fixed string to each element:

import pyarrow as pa
import pyarrow.compute as pc

t = pa.table({"a": ["one", "two", "three"]})

t = t.set_column(0, "a", pc.binary_join_element_wise(t["a"], "_frobenius", ""))

print(t)

Output:

pyarrow.Table
a: string
----
a: [["one_frobenius","two_frobenius","three_frobenius"]]

You might convert to the pandas Dataframe, modify the strings, and convert back. For example,

>>> import pyarrow as pa
>>> t = pa.table({'a': ['one', 'two', 'three']})
>>> df = t.to_pandas()
>>> df
       a
0    one
1    two
2  three
>>> df['a'] = df['a'] + '_frobenius'
>>> df
                 a
0    one_frobenius
1    two_frobenius
2  three_frobenius
>>> new_table = t.set_column(0, 'a', pa.array(df['a']))
>>> new_table
pyarrow.Table
a: string
----
a: [["one_frobenius","two_frobenius","three_frobenius"]]