@@ -164,27 +164,27 @@ def test_str_cat(self, box):
164164
165165 # single array
166166 result = s .str .cat ()
167- exp = 'aabbc'
168- assert result == exp
167+ expected = 'aabbc'
168+ assert result == expected
169169
170170 result = s .str .cat (na_rep = '-' )
171- exp = 'aabbc-'
172- assert result == exp
171+ expected = 'aabbc-'
172+ assert result == expected
173173
174174 result = s .str .cat (sep = '_' , na_rep = 'NA' )
175- exp = 'a_a_b_b_c_NA'
176- assert result == exp
175+ expected = 'a_a_b_b_c_NA'
176+ assert result == expected
177177
178178 t = np .array (['a' , np .nan , 'b' , 'd' , 'foo' , np .nan ], dtype = object )
179- exp = box (['aa' , 'a-' , 'bb' , 'bd' , 'cfoo' , '--' ])
179+ expected = box (['aa' , 'a-' , 'bb' , 'bd' , 'cfoo' , '--' ])
180180
181181 # Series/Index with array
182182 result = s .str .cat (t , na_rep = '-' )
183- assert_series_or_index_equal (result , exp )
183+ assert_series_or_index_equal (result , expected )
184184
185185 # Series/Index with list
186186 result = s .str .cat (list (t ), na_rep = '-' )
187- assert_series_or_index_equal (result , exp )
187+ assert_series_or_index_equal (result , expected )
188188
189189 # errors for incorrect lengths
190190 rgx = 'All arrays must be same length, except those having an index.*'
@@ -217,30 +217,30 @@ def test_str_cat_categorical(self, box, dtype_caller, dtype_target):
217217 s = s if box == Index else Series (s , index = s )
218218 t = Index (['b' , 'a' , 'b' , 'c' ], dtype = dtype_target )
219219
220- exp = Index (['ab' , 'aa' , 'bb' , 'ac' ])
221- exp = exp if box == Index else Series (exp , index = s )
220+ expected = Index (['ab' , 'aa' , 'bb' , 'ac' ])
221+ expected = expected if box == Index else Series (expected , index = s )
222222
223223 # Series/Index with unaligned Index
224224 with tm .assert_produces_warning (expected_warning = FutureWarning ):
225225 # FutureWarning to switch to alignment by default
226226 result = s .str .cat (t )
227- assert_series_or_index_equal (result , exp )
227+ assert_series_or_index_equal (result , expected )
228228
229229 # Series/Index with Series having matching Index
230230 t = Series (t , index = s )
231231 result = s .str .cat (t )
232- assert_series_or_index_equal (result , exp )
232+ assert_series_or_index_equal (result , expected )
233233
234234 # Series/Index with Series.values
235235 result = s .str .cat (t .values )
236- assert_series_or_index_equal (result , exp )
236+ assert_series_or_index_equal (result , expected )
237237
238238 # Series/Index with Series having different Index
239239 t = Series (t .values , index = t )
240240 with tm .assert_produces_warning (expected_warning = FutureWarning ):
241241 # FutureWarning to switch to alignment by default
242242 result = s .str .cat (t )
243- assert_series_or_index_equal (result , exp )
243+ assert_series_or_index_equal (result , expected )
244244
245245 @pytest .mark .parametrize ('box' , [Series , Index ])
246246 def test_str_cat_mixed_inputs (self , box ):
@@ -250,56 +250,57 @@ def test_str_cat_mixed_inputs(self, box):
250250 t = Series (['A' , 'B' , 'C' , 'D' ], index = s .values )
251251 d = concat ([t , Series (s , index = s )], axis = 1 )
252252
253- exp = Index (['aAa' , 'bBb' , 'cCc' , 'dDd' ])
254- exp = exp if box == Index else Series (exp .values , index = s .values )
253+ expected = Index (['aAa' , 'bBb' , 'cCc' , 'dDd' ])
254+ expected = expected if box == Index else Series (expected .values ,
255+ index = s .values )
255256
256257 # Series/Index with DataFrame
257258 result = s .str .cat (d )
258- assert_series_or_index_equal (result , exp )
259+ assert_series_or_index_equal (result , expected )
259260
260261 # Series/Index with two-dimensional ndarray
261262 result = s .str .cat (d .values )
262- assert_series_or_index_equal (result , exp )
263+ assert_series_or_index_equal (result , expected )
263264
264265 # Series/Index with list of Series
265266 result = s .str .cat ([t , s ])
266- assert_series_or_index_equal (result , exp )
267+ assert_series_or_index_equal (result , expected )
267268
268269 # Series/Index with mixed list of Series/array
269270 result = s .str .cat ([t , s .values ])
270- assert_series_or_index_equal (result , exp )
271+ assert_series_or_index_equal (result , expected )
271272
272273 # Series/Index with list of list-likes
273274 with tm .assert_produces_warning (expected_warning = FutureWarning ):
274275 # nested list-likes will be deprecated
275276 result = s .str .cat ([t .values , list (s )])
276- assert_series_or_index_equal (result , exp )
277+ assert_series_or_index_equal (result , expected )
277278
278279 # Series/Index with list of Series; different indexes
279280 t .index = ['b' , 'c' , 'd' , 'a' ]
280281 with tm .assert_produces_warning (expected_warning = FutureWarning ):
281282 # FutureWarning to switch to alignment by default
282283 result = s .str .cat ([t , s ])
283- assert_series_or_index_equal (result , exp )
284+ assert_series_or_index_equal (result , expected )
284285
285286 # Series/Index with mixed list; different indexes
286287 with tm .assert_produces_warning (expected_warning = FutureWarning ):
287288 # FutureWarning to switch to alignment by default
288289 result = s .str .cat ([t , s .values ])
289- assert_series_or_index_equal (result , exp )
290+ assert_series_or_index_equal (result , expected )
290291
291292 # Series/Index with DataFrame; different indexes
292293 d .index = ['b' , 'c' , 'd' , 'a' ]
293294 with tm .assert_produces_warning (expected_warning = FutureWarning ):
294295 # FutureWarning to switch to alignment by default
295296 result = s .str .cat (d )
296- assert_series_or_index_equal (result , exp )
297+ assert_series_or_index_equal (result , expected )
297298
298299 # Series/Index with iterator of list-likes
299300 with tm .assert_produces_warning (expected_warning = FutureWarning ):
300301 # nested list-likes will be deprecated
301302 result = s .str .cat (iter ([t .values , list (s )]))
302- assert_series_or_index_equal (result , exp )
303+ assert_series_or_index_equal (result , expected )
303304
304305 # errors for incorrect lengths
305306 rgx = 'All arrays must be same length, except those having an index.*'
@@ -359,50 +360,50 @@ def test_str_cat_align_indexed(self, box, join):
359360 t = Series (['D' , 'A' , 'E' , 'B' ], index = ['d' , 'a' , 'e' , 'b' ])
360361 sa , ta = s .align (t , join = join )
361362 # result after manual alignment of inputs
362- exp = sa .str .cat (ta , na_rep = '-' )
363+ expected = sa .str .cat (ta , na_rep = '-' )
363364
364365 if box == Index :
365366 s = Index (s )
366367 sa = Index (sa )
367- exp = Index (exp )
368+ expected = Index (expected )
368369
369370 result = s .str .cat (t , join = join , na_rep = '-' )
370- assert_series_or_index_equal (result , exp )
371+ assert_series_or_index_equal (result , expected )
371372
372373 @pytest .mark .parametrize ('join' , ['left' , 'outer' , 'inner' , 'right' ])
373374 def test_str_cat_align_mixed_inputs (self , join ):
374375 s = Series (['a' , 'b' , 'c' , 'd' ])
375376 t = Series (['d' , 'a' , 'e' , 'b' ], index = [3 , 0 , 4 , 1 ])
376377 d = concat ([t , t ], axis = 1 )
377378
378- exp_outer = Series (['aaa' , 'bbb' , 'c--' , 'ddd' , '-ee' ])
379- exp = exp_outer .loc [s .index .join (t .index , how = join )]
379+ expected_outer = Series (['aaa' , 'bbb' , 'c--' , 'ddd' , '-ee' ])
380+ expected = expected_outer .loc [s .index .join (t .index , how = join )]
380381
381382 # list of Series
382383 result = s .str .cat ([t , t ], join = join , na_rep = '-' )
383- tm .assert_series_equal (result , exp )
384+ tm .assert_series_equal (result , expected )
384385
385386 # DataFrame
386387 result = s .str .cat (d , join = join , na_rep = '-' )
387- tm .assert_series_equal (result , exp )
388+ tm .assert_series_equal (result , expected )
388389
389390 # mixed list of indexed/unindexed
390391 u = np .array (['A' , 'B' , 'C' , 'D' ])
391- exp_outer = Series (['aaA' , 'bbB' , 'c-C' , 'ddD' , '-e-' ])
392+ expected_outer = Series (['aaA' , 'bbB' , 'c-C' , 'ddD' , '-e-' ])
392393 # joint index of rhs [t, u]; u will be forced have index of s
393394 rhs_idx = t .index & s .index if join == 'inner' else t .index | s .index
394395
395- exp = exp_outer .loc [s .index .join (rhs_idx , how = join )]
396+ expected = expected_outer .loc [s .index .join (rhs_idx , how = join )]
396397 result = s .str .cat ([t , u ], join = join , na_rep = '-' )
397- tm .assert_series_equal (result , exp )
398+ tm .assert_series_equal (result , expected )
398399
399400 with tm .assert_produces_warning (expected_warning = FutureWarning ):
400401 # nested list-likes will be deprecated
401402 result = s .str .cat ([t , list (u )], join = join , na_rep = '-' )
402- tm .assert_series_equal (result , exp )
403+ tm .assert_series_equal (result , expected )
403404
404405 # errors for incorrect lengths
405- rgx = 'If `others` contains arrays or lists \(or other list-likes.*'
406+ rgx = r 'If `others` contains arrays or lists \(or other list-likes.*'
406407 z = Series (['1' , '2' , '3' ]).values
407408
408409 # unindexed object of wrong length
@@ -418,14 +419,14 @@ def test_str_cat_special_cases(self):
418419 t = Series (['d' , 'a' , 'e' , 'b' ], index = [3 , 0 , 4 , 1 ])
419420
420421 # iterator of elements with different types
421- exp = Series (['aaa' , 'bbb' , 'c-c' , 'ddd' , '-e-' ])
422+ expected = Series (['aaa' , 'bbb' , 'c-c' , 'ddd' , '-e-' ])
422423 result = s .str .cat (iter ([t , s .values ]), join = 'outer' , na_rep = '-' )
423- tm .assert_series_equal (result , exp )
424+ tm .assert_series_equal (result , expected )
424425
425426 # right-align with different indexes in others
426- exp = Series (['aa-' , 'd-d' ], index = [0 , 3 ])
427+ expected = Series (['aa-' , 'd-d' ], index = [0 , 3 ])
427428 result = s .str .cat ([t .loc [[0 ]], t .loc [[3 ]]], join = 'right' , na_rep = '-' )
428- tm .assert_series_equal (result , exp )
429+ tm .assert_series_equal (result , expected )
429430
430431 def test_cat_on_filtered_index (self ):
431432 df = DataFrame (index = MultiIndex .from_product (
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