pandas.Series.str.cat   Series.str.cat(others=None, sep=None, na_rep=None, join='left')[source]
 
Concatenate strings in the Series/Index with given separator. If others is specified, this function concatenates the Series/Index and elements of others element-wise. If others is not passed, then all values in the Series/Index are concatenated into a single string with a given sep.  Parameters 
 
others:Series, Index, DataFrame, np.ndarray or list-like


Series, Index, DataFrame, np.ndarray (one- or two-dimensional) and other list-likes of strings must have the same length as the calling Series/Index, with the exception of indexed objects (i.e. Series/Index/DataFrame) if join is not None. If others is a list-like that contains a combination of Series, Index or np.ndarray (1-dim), then all elements will be unpacked and must satisfy the above criteria individually. If others is None, the method returns the concatenation of all strings in the calling Series/Index.  
sep:str, default ‘’


The separator between the different elements/columns. By default the empty string ‘’ is used.  
na_rep:str or None, default None


Representation that is inserted for all missing values:  If na_rep is None, and others is None, missing values in the Series/Index are omitted from the result. If na_rep is None, and others is not None, a row containing a missing value in any of the columns (before concatenation) will have a missing value in the result.   
join:{‘left’, ‘right’, ‘outer’, ‘inner’}, default ‘left’


Determines the join-style between the calling Series/Index and any Series/Index/DataFrame in others (objects without an index need to match the length of the calling Series/Index). To disable alignment, use .values on any Series/Index/DataFrame in others.  New in version 0.23.0.   Changed in version 1.0.0: Changed default of join from None to ‘left’.     Returns 
 str, Series or Index

If others is None, str is returned, otherwise a Series/Index (same type as caller) of objects is returned.      See also  split

Split each string in the Series/Index.  join

Join lists contained as elements in the Series/Index.    Examples When not passing others, all values are concatenated into a single string: 
>>> s = pd.Series(['a', 'b', np.nan, 'd'])
>>> s.str.cat(sep=' ')
'a b d'
  By default, NA values in the Series are ignored. Using na_rep, they can be given a representation: 
>>> s.str.cat(sep=' ', na_rep='?')
'a b ? d'
  If others is specified, corresponding values are concatenated with the separator. Result will be a Series of strings. 
>>> s.str.cat(['A', 'B', 'C', 'D'], sep=',')
0    a,A
1    b,B
2    NaN
3    d,D
dtype: object
  Missing values will remain missing in the result, but can again be represented using na_rep 
>>> s.str.cat(['A', 'B', 'C', 'D'], sep=',', na_rep='-')
0    a,A
1    b,B
2    -,C
3    d,D
dtype: object
  If sep is not specified, the values are concatenated without separation. 
>>> s.str.cat(['A', 'B', 'C', 'D'], na_rep='-')
0    aA
1    bB
2    -C
3    dD
dtype: object
  Series with different indexes can be aligned before concatenation. The join-keyword works as in other methods. 
>>> t = pd.Series(['d', 'a', 'e', 'c'], index=[3, 0, 4, 2])
>>> s.str.cat(t, join='left', na_rep='-')
0    aa
1    b-
2    -c
3    dd
dtype: object
>>>
>>> s.str.cat(t, join='outer', na_rep='-')
0    aa
1    b-
2    -c
3    dd
4    -e
dtype: object
>>>
>>> s.str.cat(t, join='inner', na_rep='-')
0    aa
2    -c
3    dd
dtype: object
>>>
>>> s.str.cat(t, join='right', na_rep='-')
3    dd
0    aa
4    -e
2    -c
dtype: object
  For more examples, see here.