Getting only element from a single-element list in Python?

by

Raises exception if not exactly one item:

Sequence unpacking:

singleitem, = mylist
# Identical in behavior (byte code produced is the same),
# but arguably more readable since a lone trailing comma could be missed:
[singleitem] = mylist

Rampant insanity, unpack the input to the identity lambda function:

# The only even semi-reasonable way to retrieve a single item and raise an exception on
# failure for too many, not just too few, elements as an expression, rather than a
# statement, without resorting to defining/importing functions elsewhere to do the work
singleitem = (lambda x: x)(*mylist)

All others silently ignore spec violation, producing first or last item:

Explicit use of iterator protocol:

singleitem = next(iter(mylist))

Destructive pop:

singleitem = mylist.pop()

Negative index:

singleitem = mylist[-1]

Set via single iteration for (because the loop variable remains available with its last value when a loop terminates):

for singleitem in mylist: break

There are many others (combining or varying bits of the above, or otherwise relying on implicit iteration), but you get the idea.

More Related Contents:

  1. What do ellipsis […] mean in a list?
  2. Why is a list comprehension so much faster than appending to a list?
  3. How to apply a function to each sublist of a list in python?
  4. Skip elements on a condition based in a list comprehension in python
  5. Converting string to tuple without splitting characters
  6. Is there a way to ordinate numbers in a list?
  7. Python Variable Declaration
  8. Integer division in Python 2 and Python 3
  9. Extracting text from a PDF file using PDFMiner in python?
  10. Changing an element in one list changes multiple lists [duplicate]
  11. How to get the latest file in a folder?
  12. Check if all elements of a list are of the same type
  13. What’s the difference between __builtin__ and __builtins__?
  14. Most pythonic way to interleave two strings
  15. Argparse with required subparser
  16. Search for a value in a nested dictionary python
  17. portable way to write csv file in python 2 or python 3
  18. How to run different python versions in cmd [duplicate]
  19. What is a clean way to convert a string percent to a float?
  20. Using Properties in Python classes cause “maximum recursion depth exceeded” [duplicate]
  21. How do I return dictionary keys as a list in Python?
  22. Python: Splat/unpack operator * in python cannot be used in an expression?
  23. Sound generation / synthesis with python?
  24. Calling Python script from C++ and using its output
  25. What are the differences between bool() and operator.truth()?
  26. Deleting consonants from a string in Python
  27. Type error Unhashable type:set
  28. Run process with realtime output to a Tkinter GUI
  29. Size of a Python list in memory
  30. What does the slice() function do in Python?

Leave a Comment