gives expr with elem appended.


represents an operator form of Append that can be applied to an expression.


  • In iteratively building a list, it is usually more efficient to use Sow and Reap than to use Append[list,new] at each step.
  • Append works on SparseArray objects, returning ordinary lists if necessary.
  • Append can be used on Association objects. Single new elements are specified in the form key->value. New values replace older ones if their keys are the same.
  • Multiple elements to append to an association can be specified in the form {key1->value1,key2->value2, }.
  • Append[elem][expr] is equivalent to Append[expr,elem].


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Basic Examples  (3)

Append to an Association:

Append several rules to an Association:

Generalizations & Extensions  (1)

Use a head other than List:

Applications  (4)

Append a row to a matrix:

Append to each row in a matrix:

Append a vector to a matrix:

Successively append to a list:

Possible Issues  (2)

When working on a shared list in parallel, Append is not atomic (or thread-safe):

Use AppendTo in such circumstances:

Wolfram Research (1988), Append, Wolfram Language function, (updated 2014).


Wolfram Research (1988), Append, Wolfram Language function, (updated 2014).


Wolfram Language. 1988. "Append." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2014.


Wolfram Language. (1988). Append. Wolfram Language & System Documentation Center. Retrieved from


@misc{reference.wolfram_2024_append, author="Wolfram Research", title="{Append}", year="2014", howpublished="\url{}", note=[Accessed: 24-April-2024 ]}


@online{reference.wolfram_2024_append, organization={Wolfram Research}, title={Append}, year={2014}, url={}, note=[Accessed: 24-April-2024 ]}