- Update to 1.7.1:
  core
  * There was a regression in 1.7 that meant that __slots__ 
    would not work correctly for Basic instances and they 
    would end up having __dict__. This also made it possible 
    to set arbitrary attributes on Basic instances such as 
    symbols which breaks immutability. This was fixed in 
    1.7.1 to ensure that Basic instances do not have 
    __dict__ and it is not possible to set attributes on 
    them. (#20590 by @oscarbenjamin) s
  series
  * Fixed lazy iteration of series with expr.series(x, 
     n=None) which was broken in the 1.7 release. (#20589 by 
     @oscarbenjamin and @sachin-4099) 
  stats
  * Updated documentation for sympy.stats.sample for seed 
    argument. (#20555 by @czgdp1807)
  * sympy.stats.sample now has an optional seed argument. 
    (#20528 by @czgdp1807)
  * Random failures with sympy.stats.sample have now been 
    fixed. (#20527 by @czgdp180
- Changelog for 1.7.0:
  Backwards compatibility breaks and deprecations
  -----------------------------------------------
  core
  * Modules and names that were accidentally importable from 
    sympy are no longer importable. In sympy 1.6 importing and 
    using these names would give a deprecation warning. In 
    sympy 1.7 these names are removed. As an example from 
    sympy import add would need to be from sympy.core import 
    add or import sympy.core.add as add. (#19554 by 
    @oscarbenjamin)
  * DEPRECATION: Using non-Expr args in Add, Mul or Pow is 
    now deprecated (#19445 by @oscarbenjamin)
  diffgeom
  * Manifold.patches attribute is deprecated. (#19368 by 
    @JSS95 and @mcpl-sympy)
  * Patch.coord_systems attribute is deprecated. (#19368 by 
    @JSS95 and @mcpl-sympy)
  * Class signature names of CoordSystem is deprecated.  
    CoordinateSymbol class and CoordSystem.symbols attribute are 
    introduced instead. (#19368 by @JSS95 and @mcpl-sympy)
  * CoordSystem.transforms, CoordSystem.connect_to, and 
    CoordSystem.coord_tuple_transform_to are deprecated. Class 
    signature relations, CoordSystem.transformation and 
    CoordSystem.transform are introduced instead. (#19368 by 
    @JSS95 and @mcpl-sympy)
  printing
  * sympy.printing.pretty.pretty_symbology.xstr has been 
    deprecated (#20081 by @eric-wieser)
  * The unicode argument to sympy.printing.stringpict.prettyForm 
    has been deprecated (#20081 by @eric-wieser)
  * The deprecation of calling preview with viewer="StringIO" is 
    now expired instead of forgotten (a regression in 1.6.0) 
    (#19905 by @eric-wieser)
  * The modules sympy.printing.ccode, sympy.printing.fcode, and 
    sympy.printing.cxxcode have been renamed to sympy.printing.c, 
    sympy.printing.fortran, and sympy.printing.cxx, respectively. 
    This was done to avoid conflicts that occur when a module name 
    is the same as a function name. The modules are still 
    importable under their old names but doing so is deprecated 
    and a warning will be given (#19908 by @asmeurer)
  * from sympy.printing.codeprinter import Assignment no longer 
    works. You should use from sympy.codegen import Assignment, 
    which is where Assignment has lived since SymPy 1.1. (#19908 
    by @asmeurer)
  * Calling preview with viewer="file" no longer looks for a file 
    executable (a regression in 1.6.0) (#19905 by @eric-wieser)
  solvers
  * solve_linear_system is now a thin wrapper for linsolve. It is 
    recommended to use linsolve in new code. solve_linear_system 
    maybe deprecated or removed in future. (#18814 by 
    @oscarbenjamin)
  utilities
  * find_executable is deprecated in favor of the builtin shutil.
    which. (#19634 by @eric-wieser)
  Changes
  -------
  algebras
  * Added DocString for integrate function of quaternion class. 
    (#19410 by @mohitshah3111999)
  codegen
  * Added support for generating calls to scipy.special.cosm1. 
    (#20011 by @bjodah)
  * sympy.codegen and sympy.combinatorics are no longer imported 
    as part of from sympy import *. The codegen and combinatorics 
    modules do not have any names that are included in the 
    top-level namespace, so their being imported with the 
    top-level SymPy was a mistake. This improves the import time 
    of from sympy import *. (#19908 by @asmeurer)
  * Added support for generating calls to numpy.logaddexp & numpy.
    logaddexp2. (#19880 by @bjodah)
  * Fix bugs to the parser of matrix expressions in order to build 
    CodegenArray objects correctly. (#19197 by @Upabjojr)
  combinatorics
  * Fixed a bug in PermutationGroup.minimal_blocks caused by 
    modifying a list while iterating over its indices. (#19954 by 
    @ilya-pchelintsev)
  concrete
  * Implemented Raabe's Test (#18656 by @sachin-4099)
  core
  * Fixed a few broken cases of expr.is_integer (#20450 by @coproc 
    and @tbennun)
  * Modules and names that were accidentally importable from sympy 
    are no longer importable. In sympy 1.6 importing and using 
    these names would give a deprecation warning. In sympy 1.7 
    these names are removed. As an example from sympy import add 
    would need to be from sympy.core import add or import sympy.
    core.add as add. (#19554 by @oscarbenjamin)
  * Zero raised to power Negative Infinity gives ComplexInfinity
    (zoo) instead of zero (#20212 by @sidhu1012)
  * Extensible add, mul and power functions are introduced to 
    allow sympy objects to define what classes should be used for 
    them in place of Add, Mul and Pow (e.g. matrices use MatAdd). 
    This is an experimental approach aimed at enabling the     
    behaviour of core routines (expand, collect, etc) to be 
    customised by user-defined types (e.g. MatAdd rather than 
    Add). This mechanism is still experimental, is not fully 
    implemented across the core and might be changed or removed in 
    a future release of sympy. (#19463 by @JSS95 and @mcpl-sympy)
  * divmod on sympy.Float with 0 numerator now results in (0, 0). 
    (#20109 by @eriknw)
  * Dict operations no longer automatically converts strings into 
    SymPy types. (#19911 by @asmeurer)
  * Dict operations no longer raise SympifyError. (#19911 by 
    @asmeurer)
  * Fixes _eval_nseries() function of power.py (#19508 by 
    @sachin-4099)
  * Remove optional dependency on fastcache (#19492 by @pbrady)
  * DEPRECATION: Using non-Expr args in Add, Mul or Pow is now 
    deprecated (#19445 by @oscarbenjamin)
  * When creating an Add or Mul with evaluate=False identities (0 
    or 1) are no longer removed. (#19450 by @oscarbenjamin)
  * Fixes _eval_nseries() function of mul.py (#19369 by 
    @sachin-4099)
  * Sum is now included in count_ops results (#19261 by @smichr)
  * match has been optimized to improve term-matching in Add 
    (#19261 by @smichr)
  * match will automatically ignore bound symbols when matching 
    (#19261 by @smichr)
  * match results will no longer contain extraneous symbols (only 
    those requested) (#19261 by @smichr)
  * as_dummy should give a canonical result for expressions having 
    bound symbols (#19261 by @smichr)
  * Lambdas written in terms of different symbols will no longer 
    compare equal; this was an abuse of the Python == operator 
    (#19261 by @smichr)
  * expr: A new method is_meromorphic is added. (#19306 by @jksuom)
  diffgeom
  * Manifold.patches attribute is deprecated. (#19368 by @JSS95 
    and @mcpl-sympy)
  * Patch.coord_systems attribute is deprecated. (#19368 by @JSS95 
    and @mcpl-sympy)
  * Class signature names of CoordSystem is deprecated. 
    CoordinateSymbol class and CoordSystem.symbols attribute are 
    introduced instead. (#19368 by @JSS95 and @mcpl-sympy)
  * CoordSystem.transforms, CoordSystem.connect_to, and 
    CoordSystem.coord_tuple_transform_to are deprecated. Class 
    signature relations, CoordSystem.transformation and 
    CoordSystem.transform are introduced instead. (#19368 by 
    @JSS95 and @mcpl-sympy)
  * CoordSystem.jacobian_determinant method is introduced. (#19368 
    by @JSS95 and @mcpl-sympy)
  functions
  * lambdify added a warning when args is a set. (#19792 by 
    @foice, @RobertoFranceschini, and @sylee957)
  * Fixes _eval_nseries method of log (#20002 by @sachin-4099)
  * Adds _eval_is_meromorphic method and _eval_aseries to class 
    lowergamma (#19990 by @sachin-4099)
  * Adds _eval_is_meromorphic method and 
    _eval_rewrite_as_tractable method to class uppergamma (#19990 
    by @sachin-4099)
  * Rectifies eval method of class besselk (#19990 by @sachin-4099)
  * Adds _eval_is_meromorphic to bessel function. (#19963 by 
    @sachin-4099)
  * Adds _eval_nseries function to sin and cos. (#19916 by 
    @sachin-4099)
  * reduced symbolic multiples of pi in trigonometric functions 
    (#19741 by @sachin-4099)
  * fixed errors in assumptions when rewriting RisingFactorial / 
    FallingFactorial as gamma or factorial (#18696 by @sachin-4099)
  * Adds _singularities to LambertW function (#19716 by 
    @sachin-4099)
  * Rectifies _eval_rewrite_as_tractable method of class erf 
    (#19697 by @sachin-4099)
  * Improved condition checking in piecewise_simplify() (#19596 by 
    @dhruvmendiratta6 and @smichr)
  * Implemented _eval_rewrite_as_Abs() for sign (#19487 by 
    @dhruvmendiratta6)
  * Adds cdir parameter to handle series expansions on branch cuts 
    (#19555 by @sachin-4099)
  * Adds _eval_rewrite_as_factorial() and _eval_rewrite_as_gamma() 
    functionalities for subfactorial (#19515 by @sachin-4099)
  * Fixed cot.as_real_imag (sign error in imaginary part) (#19468 
    by @DaveWitteMorris and @gschintgen)
  * Corrects the _eval_as_leading_term() method of tan and sec 
    functions (#19461 by @sachin-4099)
  * bsplines are more robust in terms of handling symbolic knots 
    (#19272 by @smichr)
  geometry
  * Ellipses with eccentricity >=1 and for eccentricity < 0 will 
    be handled as trivial cases (#20045 by @agrawalshubham01)
  integrals
  * upgrades to manualintegrate to support inverse trig functions! 
    (#19993 by @iammosespaulr)
  interactive
  * The _repr_latex_, _repr_svg_, and _repr_png_ methods of 
    subclasses of sympy objects are no longer discarded when 
    init_printing() is called. (#19944 by @eric-wieser)
  logic
  * Binary boolean operators on Boolean objects no longer coerce 
    strings (#20093 by @eric-wieser)
  matrices
  * Adding an array and a matrix now consistently gives TypeError. 
    (#20159 by @sidhu1012)
  * changed subs function to check if input is zip (#19159 by 
    @czgdp1807 and @gfolbe318)
  * added tests in test_commonmatrix.py (#19159 by @czgdp1807 and 
    @gfolbe318)
  * The ordering of parameters in a parametrised solution from 
    gauss_jordan_solve was fixed. Previously incorrect results 
    were returned for some underdetermined systems. (#19885 by 
    @1124816)
  * Prevents infinite recursion with rmul (#19860 by @mloubout)
  * Added class MatrixSet to represent the set of matrices (#19826 
    by @Smit-create)
  * Disabled default matrix intermediate product simplification 
    and changed it to enable via context manager. (#19588 by 
    @oscarbenjamin and @Pristine-Cat)
  * Use more efficient Cholesky factorization method to check if 
    matrices are positive semidefinite. (#19573 by @galbwe)
  * row_del and col_del will raise IndexError rather than 
    ValueError when the index is out of bounds. (#19571 by 
    @sylee957)
  * Fixed a bug in the implementation of Sylvester's criterion for 
    determining if a matrix is positive semidefinite. (#19556 by 
    @galbwe)
  * Explicit non-matrix are treated as scalar (#19533 by @mloubout)
  * QRdecomposition will return matrices with zero rows and 
    columns for zero rank matrices. e.g. Matrix([[0, 0, 0], [0, 0, 
    0], [0, 0, 0]]) will be decomposed with Matrix(3, 0, []) and 
    Matrix(0, 3, []) (#19319 by @sylee957)
  * Added Matrix.companion for creating dense companion matrix. 
    (#19339 by @sylee957)
  * Added CompanionMatrix for creating a symbolic companion 
    matrix. (#19339 by @sylee957)
  * Matrix([]).eigenvals(multiple=True) will give an empty list 
    instead of an empty dict. (#19355 by @sylee957)
  * Determinant is now considered commutative. (#19354 by 
    @eric-wieser)
  ntheory
  * Integrated Lenstra's Elliptic Curve factorization into 
    factorint (#19937 by @abh2k)
  * Added quadratic sieve (#19657 by @abh2k)
  * Implemented Lenstra's Elliptic curve factorization and 
    Elliptic curve primality test (#19436 by @abhinav28071999)
  parsing
  * Added support for while loop in C Parser (#20188 by 
    @smitgajjar)
  * Upgraded Relational Operator support (#19982 by @iammosespaulr)
  * Bra-Ket Notation support (#19982 by @iammosespaulr)
  * Improved Grammar (#19982 by @iammosespaulr)
  * added Latex support for "not equal" and expanded support for 
    less than, greater than symbols (#19970 by @bhpayne)
  * parse_latex supports \left and \right parenthesis notation. 
    (#19466 by @sylee957)
  * parse_latex can parse expressions with amsmath spacing (#19475 
    by @sylee957)
  * Added parsing of \exp in parse_latex. (#19395 by @sylee957)
  * Add more parsing rules and test examples. (#19177 by @wuyudi)
  * Added support for more data types in C parser: signed char, 
    unsigned char, short, short int, signed short, signed short 
    int, unsigned short, unsigned short int, unsigned int, long, 
    long int, signed long, signed long int, unsigned long, 
    unsigned long int, double, long double. Also, modified the 
    data type for int and float to intc and float32 respectively, 
    replacing integer and real (#19230 by @smitgajjar)
  * Added support for shorthand operators in C parser: +=, -=, *=, 
    /= and %= (#19230 by @smitgajjar)
  * Removed the assumption of value of a variable, if it is not 
    initialized while variable declaration(e.g.; in case of int a;
    , the value of a was assumed to be Integer(0), in case of 
    float b;, the value of b was assumed to be Float(0.0) and in 
    case of bool c;, the value of c was assumed to be S.false). 
    Also, removed the assumption of default value of formal 
    parameters while parameter declaration in function definition 
    or function prototype (e.g.; in case of function definition 
    void func(int a, float b) { //some code }, default value of 
    formal parametersa and b were assumed to be Integer(0) and 
    Float(0.0) respectively) (#19230 by @smitgajjar)
  physics.control
  * Added dc_gain, poles, zeros, and is_stable in TransferFunction 
    class. (#19896 by @namannimmo10)
  * Adding a new control systems toolbox as physics.control. 
    (#18436 by @benepla and @namannimmo10)
  * Add TransferFunction, Series, Parallel, and Feedback class for 
    physics.control submodule (#19390 by @benepla and 
    @namannimmo10)
  physics.quantum
  * Simplification of Dagger() * IdentityOperator() (#19783 by 
    @dhruvmendiratta6)
  * When printing, Commutator, Anticommutator, InnerProduct, 
    TensorProduct, and OuterProduct now respect keyword-arguments 
    to sstr. (#19424 by @eric-wieser)
  physics.units
  * Fixed some dimensional analysis bugs with the addition and 
    multiplication operators. (#19705 by @mgreminger)
  physics.vector
  * Added user warnings for all possible paths are found in 
    particle.py. (#20131 by @sidhu1012)
  * Added user warning for cyclic paths in particle.py. (#20131 by 
    @sidhu1012)
  * Point.vel() now attempts to calculate the velocity using the 
    relative position from other points if it has not been already 
    set by the user. This behavior mimics the existing behavior in 
    ReferenceFrame.ang_vel_in(). (#20049 by @moorepants and 
    @sidhu1012)
  * VectorLatexPrinter now respects the symbol_names setting when 
    printing dynamicsymbols (#19684 by @eric-wieser)
  * VectorLatexPrinter now know about the same trig functions as 
    the regular printer (#19684 by @eric-wieser)
  * When printing, Vector and Dyadic now respect keyword-arguments 
    to sstr and latex. As a result, these no longer use vector 
    printing customizations unless init_vprinting has been called. 
    (#19640 by @eric-wieser)
  plotting
  * capability to subclass Basebackend and specify it to the 
    plotting functions, thus creating plots with other plotting 
    libraries (#20463 by @oscarbenjamin)
    * Fixed plot3d_parametric_line plotting curves out of the box. 
    (#19252 by @sylee957)
  polys
  * Polys with complex floating point coefficients will now use 
    the CC domain rather than EX. (#20194 by @oscarbenjamin)
  * Fixed a bug in minimal_polynomial when using Groebner bases 
    (compose=False) (#19799 by @coproc)
  * Fixed GeneratorsError for creating some elements of
    FractionField when its ground domain is FractionField or PolynomialRing. (#19713 by @sylee957)
  * Fixed Poly initialized with PolyElement mutating the generator 
    of the coefficient in the form of polynomial. (e.g. Poly(ZZ[x]
    (x+1), y, domain=ZZ[x]) becomes Poly(y+1, y, domain=ZZ[x])) 
    (#19659 by @sylee957)
  * Fixed Poly initialized with FracElement raising SympifyError. 
    (e.g. dom = ZZ.frac_field(x); Poly(dom(x+2), y, domain=dom)) 
    (#19659 by @sylee957)
  * Add division to finite extensions. (#19593 by @gschintgen and 
    @jksuom)
  * Fixed GCD to always return a non-negative constant. (#19569 by 
    @KaustubhDamania)
  * added new domains for Gaussian integers and rationals (#15396 
    by @jksuom and @smichr)
  * Add the Gaussian domains ZZ_I and QQ_I to Poly. Make Poly use 
    the Gaussian domains automatically when I is present in the 
    input. Add factorisation over the Gaussian integers (ZZ_I). 
    The polys keyword argument gaussian=True now results in the 
    domain QQ_I rather than the extension field QQ<I>. (#15396 by 
    @oscarbenjamin)
  * improvement of dup_zz_mignotte_bound(f, K) by Knuth-Cohen 
    bound (#19254 by @lagamura)
  printing
  * Support frac with pycode printers (for lambdify) (#20115 by 
    @ehren)
  * Round-trip printing of floats (double-precision) to content 
    MathML. (#19958 by @lcontento)
  * latex now once again requires settings to be passed as keyword 
    and not positional arguments, and respects printer settings 
    changed with set_global_settings; restoring the behavior from 
    sympy 1.2 and earlier. (#20067 by @eric-wieser)
  * sympy.printing.pretty.pretty_symbology.xstr has been 
    deprecated (#20081 by @eric-wieser)
  * The unicode argument to sympy.printing.stringpict.prettyForm 
    has been deprecated (#20081 by @eric-wieser)
  * The unicode attribute of sympy.printing.stringpict.prettyForm 
    has been deprecated (#20081 by @eric-wieser)
  * The mpmath code printer now correctly prints the loggamma 
    function. (#19913 by @abhaydhiman)
  * Use literal suffix for 1.0 in C89CodePrinter's printing of pow 
    when the exponent is -1 (#19956 by @bjodah and @mmohrhard)
  * The modules sympy.printing.ccode, sympy.printing.fcode, and 
    sympy.printing.cxxcode have been renamed to sympy.printing.c, 
    sympy.printing.fortran, and sympy.printing.cxx, respectively. 
    This was done to avoid conflicts that occur when a module name 
    is the same as a function name. The modules are still 
    importable under their old names but doing so is deprecated 
    and a warning will be given (#19908 by @asmeurer)
  * from sympy.printing.codeprinter import Assignment no longer 
    works. You should use from sympy.codegen import Assignment,  
    which is where Assignment has lived since SymPy 1.1. (#19908 
    by @asmeurer)
  * Calling preview with viewer="file" no longer looks for a file 
    executable (a regression in 1.6.0) (#19905 by @eric-wieser)
  * The deprecation of calling preview with viewer="StringIO" is 
    now expired instead of forgotten (a regression in 1.6.0) 
    (#19905 by @eric-wieser)
  * When printing, NDimArray now respects keyword-arguments to 
    sstr (#19903 by @eric-wieser)
  * preview no longer fails with ValueError if the preamble 
    contains a % character. (#19858 by @eric-wieser)
  * Types which are not recognized by the LaTeX printer no longer 
    have their __str__ interpreted as LaTeX, and have their str(...
    ) printed as pre-formatted text as if they were printed 
    normally. This includes the builtin str type: latex("hello") 
    now results in the latex \mathtt{\text{hello}}.
  * If a custom type intends to be interpreted as latex, it should 
    define the _latex hook as described in the docs:    
    def _latex(self, printer):
        return str(self)  # indicate that the result of __str__ is LaTeX-compatible
  * To print a string containing LaTeX math using MathJax, use
    import IPython
    IPython.display.Math(string)
    (#19611 by @eric-wieser)
  * The latex printer now shows builtin floats using ...x10^... 
    notation instead of ...e... notation. (#19611 by @eric-wieser)
  * preview now throws OSError instead of SystemError if viewers 
    cannot be found. (#19818 by @eric-wieser)
  * Fixed the SciPy printer for sparse matrices (#19633 by 
    @benjaminwolba and @sylee957)
  * preview(..., output='pdf') now uses dvipdfmx instead of dvipdf 
    if available. As a result, it now works with a MiKTeX 
    installation on windows. (#19635 by @eric-wieser)
  * LatexPrinter._print is no longer called on strings which have 
    already been converted to Latex. (#19614 by @eric-wieser)
  * A new sympy.printing.defaults.Printable base class was added, 
    which is a mixin providing _repr_latex_ in terms of 
    LatexPrinter().doprint(). Any user type which subclasses this 
    will opt into init_printing. (#19425 by @eric-wieser)
  * Printing unevaluated Muls with multiple Number factors will   
    show all factors strictly in order. Identities will also be 
    shown explicitly. (#19450 by @oscarbenjamin)
  * user types that implement _latex are now printed as LaTeX when 
    embedded within builtin collections like list or dict. (#19389 
    by @eric-wieser)
  * fixed a bug where srepr function would not print dictionary 
    and set properly (#19346 by @rational-kunal)
  * tuples of one element now include the usual trailing comma 
    (#19348 by @eric-wieser)
  * mat_symbol_style='bold' no longer applies to subscripts of 
    matrix symbols (#19301 by @eric-wieser)
  series
  * Adds e.is_Pow heuristic to limits.py to improve the limit 
    evaluations of Pow objects (#19680 by @sachin-4099)
  * Changes in mrv() function of gruntz.py and cancel() function 
    of polytools.py resolves RecursionError and Timeout in limit 
    evaluations (#19646 by @sachin-4099)
  * modified order.py to better work with Add objects. (#19546 by 
    @maurogaravello)
  * Adds a functionality to the doit() method of limits.py which 
    uses is_meromorphic() for limit evaluations (#19432 by 
    @sachin-4099)
  * Fixed wrong computations of fourier_series for even or odd 
    functions with limits that are specified non-central. (#19382 
    by @sylee957)
  * Replaces xreplace() with subs() in rewrite() function of 
    gruntz.py resolving incorrect limit evaluations (#19297 by 
    @sachin-4099)
  * Adds a condition to limitinf() function of gruntz.py resolving 
    incorrect limit evaluations (#19292 by @sachin-4099)
  sets
  * Earlier expr and sets were treated equal which gave incorrect 
    output for some set functions(mainly : - in, is_subset), made 
    sets and expr not to be equal (#20208 by @sidhu1012)
  * nested multi-symbol first arg for ConditionSet now handled 
    with subs/as_dummy (#19512 by @smichr)
  * the bound symbols cannot be replaced with subs (#19512 by 
    @smichr)
  * the error checking for mismatched signatures for sym and the 
    base set has been improved (#19512 by @smichr)
  * ConditionSet still tries to unify symbols and denest a base 
    set that is given as a ConditionSet but will no longer 
    introduce new symbols (and will leave the base set a a 
    ConditionSet) when this cannot be done (#19512 by @smichr)
  * Fixed ConditionSet.dummy_eq() and ConditionSet.as_dummy(). 
    (#19502 by @gschintgen)
  * Fixed ConditionSet.subs() in the case where the substitution 
    targets a free symbol. (#19495 by @gschintgen)
  * Fixed _infimum_key sorting key. (#19437 by @gschintgen)
  * ImageSets with Lambdas having different symbols will no longer 
    compare equal and should be compared like a.dummy_eq(b) #19261 
    by @smichr)
  simplify
  * Fixed sqrtdenest giving wrong results for some forms of sqrt(a 
    + b*sqrt(r)) (#19932 by @sylee957)
  * Fixes a bug in collect when collection keys are not 
    independent. (#19720 by @mloubout)
  * Improved simplification for sign() (#19596 by 
    @dhruvmendiratta6 and @smichr)
  * Improved trigsimp for hyperbolic functions nested in non-trig 
    functions. (#19548 by @gschintgen)
  * Fixes a bug in collect when collected symbols appear in the 
    facorized expression. (#19431 by @mloubout)
  solvers
  * Added simplification strategies for simplifying the solutions 
    of systems of ODEs (#19998 by @mijo2 and @oscarbenjamin)
  * Fix bug in nonlinsolve leading to key-error (#19189 by 
    @nsfinkelstein and @oscarbenjamin)
  * improved functionality for solveset in case of inequalities 
    (#19978 by @maurogaravello)
  * Handling of inequalities involving Piecewise is improved in 
    solveset. (#19986 by @maurogaravello)
  * Solving higher-order system of ODEs by reducing/transforming 
    it into the first-order system of ODEs by numerous methods. 
    (#19838 by @mijo2)
  * Added component division technique to divide the system of 
    ODEs into logical sub-systems and solving each of these 
    separately. (#19762 by @mijo2)
  * Extending checkodesol and constants_renumber to handle system 
    of ODEs (#19733 by @mijo2)
  * Added dsolve_system that can solve a system of ODEs (#19695 by 
    @mijo2)
  * API for the _linear_neq_order1_type1-4 was changed to make it 
    easier for anyone to access the solver (#19653 by @mijo2)
  * Solving linear systems particularly involving polynomial 
    coefficients is much faster (#18844 by @oscarbenjamin)
  * Added the new n equations linear first-order non-constant 
    coefficient non-homogeneous solver where the coefficient 
    matrix of the system of ODEs is commutative with its 
    antiderivative. (#19594 by @mijo2)
  * solveset will always use a symbol that has only either the 
    real or complex attribute and no other attribute; when a 
    ConditionSet is returned, the original symbol for which the 
    solution is being sought will be used if it does not cause 
    evaluation of the result. (#19512 by @smichr)
  * In dsolve there is no a general solver that can solve systems 
    of constant coefficient non-homogeneous first order ODEs of 
    any size in terms of integrals. (#19341 by @mijo2)
  * Fixed exception handling in solveset's secondary trigonometric 
    solver. (#19566 by @gschintgen)
  * equations with an additive generator are now solved more 
    quickly (#19524 by @smichr)
  * Improved solveset capabilities for solving trigonometric 
    equations, notably rational and symbolic coefficients are now 
    supported. (#19507 by @gschintgen)
  * solve_linear_system is now a thin wrapper for linsolve. It is 
    recommended to use linsolve in new code. solve_linear_system 
    maybe deprecated or removed in future. (#18814 by 
    @oscarbenjamin)
  * Addition of a solver that handles a subclass of linear first 
    order non-constant coefficient homogeneous systems of ODEs 
    with any number of equations. (#19185 by @mijo2)
  stats
  * The state space of ContinuousMarkovChain is now by default a 
    Range object instead of S.Reals. (#20150 by @czgdp1807 and 
    @naveensaigit)
  * The generator matrix of ContinuousMarkovChain is now by 
    default a MatrixSymbol object instead of None. (#20150 by 
    @czgdp1807 and @naveensaigit)
  * RandomMatrixSymbol.doit will be invariant upon call. (#20136 
    by @sylee957) 
  * The state space of DiscreteMarkovChain is now by default a 
    Range object instead of S.Reals. (#20042 by @Maelstrom6)
  * The transition probability matrix of DiscreteMarkovChain is 
    now by default a MatrixSymbol object instead of None. (#20042 
    by @Maelstrom6)
  * Fixed xreplace infinitely expanding random matrix ensemble 
    classes. (#20018 by @sylee957)
  * All the ensemble classes (RandomMatrixEnsemble, 
    GaussianEnsemble, GaussianOrthogonalEnsemble, ...) now becomes 
    stub function constructors. If you want to use them as 
    classes, you should import them as RandomMatrixEnsembleModel, 
    GaussianEnsembleModel, ... (#20018 by @sylee957)
  * Added sampling of Joint RVs from external libraries (#19848 by 
    @Smit-create)
  * Added sampling for Matrix Distributions (#19857 by 
    @Smit-create)
  * Allowing CompoundDistribution to handle more than one random 
    variables (#19808 by @Smit-create)
  * Added Wishart and MatrixNormal Distributions (#19795 by 
    @Smit-create)
  * Change in return type of P and E with evaluate=False. With    
    evaluate=False, P and E are made to return Probability and 
    Expectation object respectively. (#19819 by @Smit-create)
  * Added MatrixGamma Distribution (#19734 by @Smit-create)
  * Added symbolic classes of Moment and CentralMoment (#19724 by 
    @Smit-create)
  * Added support for Compound Distributions (#19648 by 
    @Smit-create)
  * Added doit in class Probability (#19696 by @Smit-create)
  * Added MutlivariateNormal and MutlivariateLaplace function 
    (#19631 by @Smit-create)
  * Added Poisson, Wiener and Gamma Processes (#19387 by 
    @Smit-create)
  * Added Expectation Matrix, Variance Matrix and CrossCovariance 
    Matrix (#19529 by @Smit-create)
  * Added sample_stochastic for sampling from stochastic 
    processes. (#19500 by @Smit-create)
  * FIxes free_symbols method of RandomIndexedSymbol (#19459 by 
    @Smit-create)
  * Added Sampling from external libraries for all the random 
    variables of sympy (#19342 by @Smit-create)
  * Added doit method in Expectation and made E to call 
    Expectation (#19290 by @Smit-create)
  * Added is_random in sympy.stats.rv to check if expression 
    contains random variables (#19304 by @Smit-create)
  * expand added in sympy.stats.symbolic_rv API. (#19295 by 
    @Smit-create)
  * Added Lomax and Bounded pareto distribution (#19273 by 
    @Smit-create)
  * Added sampling methods for continuous variables (#18754 by 
    @Smit-create)
  * Added library option in sample (#18754 by @Smit-create)
  * sample returns an iterator object since version 1.7 (#18754 by 
    @Smit-create)
  tensor
  * Adding ArrayDerivative class as subclass of Derivative. This 
    new handles derivatives involving non-scalar expressions. 
    (#20072 by @Upabjojr)
  utilities
  * sympy.utilities.iterables.partitions() no longer reuses the 
    same dictionary for each yielded output. (#20154 by @asmeurer)
  * Add support for Integral with lambdify (using scipy or mpmath) 
    (#20134 by @ehren)
  * Lambdifying an expression with loggamma using mpmath no longer 
    raises ImportError. (#19913 by @abhaydhiman)
  * find_executable is deprecated in favor of the builtin shutil.
    which. (#19634 by @eric-wieser)
  vector
  * integral of parametric region depends on the order of limits 
    at the time of initialization. (#20044 by @friyaz)
  * vector_integrate can integrate over ImplicitRegion objects. 
    (#19883 by @friyaz)
  * Added a function to find a rational point on conic (#19807 by 
    @friyaz and @Upabjojr)
  * Added support to create implictly defined regions. (#19681 by 
    @friyaz)
  * Added support to integrate scalar/vector fields over objects 
    of geometry module. (#19650 by @friyaz)
  * added class to represent integral of scalar/vector field over 
    a parametric surface. (#19539 by @friyaz)
  * Modified API of ParametricIntegral class (#19580 by @friyaz)
  * Added class to represent a parametric region in space. (#19472 
    by @friyaz)
  other
  * The LaTeX docs now need to built with xelatex rather than 
    pdflatex. (#20309 by @oscarbenjamin)
  * Support for Python 3.5 has been dropped. SymPy now requires 
    Python 3.6 or newer. (#20145 by @oscarbenjamin)
  * more function raise TypeError when passed invalid 
    keyword-arguments, rather than ignoring them silently (#20086 
    by @eric-wieser)
  * assert sympy.testing.pytest.raises(Exception, func) no longer 
    always asserts when pytest is not present (#20012 by 
    @eric-wieser)
  * Make SymPy do less at import time so that import sympy is 
    faster. (#19910 by @asmeurer)
  * Improve code quality by cleaning the doctests up (#19406 by 
    @InCogNiTo124 and @oscarbenjamin)
  * intersphinx links to :mod:`sympy` no longer point to the 
   documentation for Immutable Matrices (#19430 by @eric-wieser)

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