gh-35920: replace basestring by str in cython files
    
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just removing this trace of python2

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URL: #35920
Reported by: Frédéric Chapoton
Reviewer(s): Matthias Köppe

Author: Release Manager

src/sage/algebras/letterplace/free_algebra_letterplace.pyx

@@ -861,7 +861,7 @@ cdef class FreeAlgebra_letterplace(Algebra):
             (2)*y*y*y + z*z + t*y
 
         """
-        if isinstance(x, basestring):
+        if isinstance(x, str):
             from sage.misc.sage_eval import sage_eval
             return sage_eval(x, locals=self.gens_dict())
         try:

src/sage/libs/gap/libgap.pyx

@@ -310,7 +310,7 @@ class Gap(Parent):
             return make_GapElement_Boolean(self, GAP_True if x else GAP_False)
         elif isinstance(x, int):
             return make_GapElement_Integer(self, make_gap_integer(x))
-        elif isinstance(x, basestring):
+        elif isinstance(x, str):
             return make_GapElement_String(self, make_gap_string(x))
         elif isinstance(x, Path):
             return make_GapElement_String(self, make_gap_string(str(x)))
@@ -398,7 +398,7 @@ class Gap(Parent):
         """
         cdef GapElement elem
 
-        if not isinstance(gap_command, basestring):
+        if not isinstance(gap_command, str):
             gap_command = str(gap_command._libgap_init_())
 
         initialize()

src/sage/libs/mpmath/ext_main.pyx

@@ -176,7 +176,7 @@ cdef int MPF_set_any(MPF *re, MPF *im, x, MPopts opts, bint str_tuple_ok) except
             elif len(x) == 4:
                 MPF_set_tuple(re, x)
                 return 1
-        if isinstance(x, basestring):
+        if isinstance(x, str):
             try:
                 st = libmp.from_str(x, opts.prec,
                     rndmode_to_python(opts.rounding))
@@ -1007,7 +1007,7 @@ cdef class Context:
             if not p % q:
                 return p // q, 'Z'
             return rationallib.mpq((p,q)), 'Q'
-        if isinstance(x, basestring) and '/' in x:
+        if isinstance(x, str) and '/' in x:
             p, q = x.split('/')
             p = int(p)
             q = int(q)

src/sage/matrix/args.pyx

@@ -1260,7 +1260,7 @@ cdef class MatrixArgs:
         if isinstance(self.entries, MatrixArgs):
             # Prevent recursion
             return MA_ENTRIES_UNKNOWN
-        if isinstance(self.entries, basestring):
+        if isinstance(self.entries, str):
             # Blacklist strings, we don't want them to be considered a sequence
             return MA_ENTRIES_UNKNOWN
         try:
@@ -1300,7 +1300,7 @@ cdef class MatrixArgs:
             return MA_ENTRIES_SEQ_FLAT
         if isinstance(x, Element) and element_is_scalar(<Element>x):
             return MA_ENTRIES_SEQ_FLAT
-        if isinstance(x, basestring):
+        if isinstance(x, str):
             # Blacklist strings, we don't want them to be considered a sequence
             return MA_ENTRIES_UNKNOWN
         try:

src/sage/matrix/matrix2.pyx

@@ -12437,7 +12437,7 @@ cdef class Matrix(Matrix1):
         R = self.base_ring()
         if not is_Vector(v):
             raise TypeError('first input should be a vector, not {0}'.format(v))
-        if not (var is None  or isinstance(var, basestring)):
+        if not (var is None  or isinstance(var, str)):
             generator = False
             try:
                 generator = var.is_gen()

src/sage/misc/cachefunc.pyx

@@ -2210,7 +2210,7 @@ cdef class CachedMethodCallerNoArgs(CachedFunction):
 
         """
         # initialize CachedFunction
-        if isinstance(f,basestring):
+        if isinstance(f,str):
             try:
                 F = getattr(inst.__class__,f)
             except AttributeError:

src/sage/misc/citation.pyx

@@ -91,7 +91,7 @@ def get_systems(cmd):
              "Rebuild Sage with the environment variable 'SAGE_PROFILE=yes' "
              "to enable profiling.")
 
-    if not isinstance(cmd, basestring):
+    if not isinstance(cmd, str):
         raise TypeError("command must be a string")
 
     from sage.repl.preparse import preparse

src/sage/misc/lazy_import.pyx

@@ -1104,7 +1104,7 @@ def lazy_import(module, names, as_=None, *,
     """
     if as_ is None:
         as_ = names
-    if isinstance(names, basestring):
+    if isinstance(names, str):
         names = [names]
         as_ = [as_]
     else:

src/sage/misc/lazy_string.pyx

@@ -205,7 +205,7 @@ cdef class _LazyString():
 
     cdef val(self):
         cdef f = self.func
-        if isinstance(f, basestring):
+        if isinstance(f, str):
             return f % self.args
         return PyObject_Call(f, self.args, self.kwargs)
 

src/sage/rings/integer.pyx

@@ -1902,7 +1902,7 @@ cdef class Integer(sage.structure.element.EuclideanDomainElement):
             sage: b'hi' * 8 == b'hihihihihihihihi'
             True
         """
-        if isinstance(s, (list, tuple, basestring, bytes)):
+        if isinstance(s, (list, tuple, str, bytes)):
             if mpz_fits_slong_p(self.value):
                 return s * mpz_get_si(self.value)
             else: