Pass list to function by value [duplicate]

by

You can use [:], but for list containing lists(or other mutable objects) you should go for copy.deepcopy():

lis[:] is equivalent to list(lis) or copy.copy(lis), and returns a shallow copy of the list.

In [33]: def func(lis):
    print id(lis)
   ....:     

In [34]: lis = [1,2,3]

In [35]: id(lis)
Out[35]: 158354604

In [36]: func(lis[:])
158065836

When to use deepcopy():

In [41]: lis = [range(3), list('abc')]

In [42]: id(lis)
Out[42]: 158066124

In [44]: lis1=lis[:]

In [45]: id(lis1)
Out[45]: 158499244  # different than lis, but the inner lists are still same

In [46]: [id(x) for x in lis1] = =[id(y) for y in lis]
Out[46]: True

In [47]: lis2 = copy.deepcopy(lis)  

In [48]: [id(x) for x in lis2] == [id(y) for y in lis]  
Out[48]: False

More Related Contents:

  1. Passing an integer by reference in Python
  2. Passing values in Python [duplicate]
  3. Python : When is a variable passed by reference and when by value? [duplicate]
  4. python pandas dataframe, is it pass-by-value or pass-by-reference
  5. Emulating pass-by-value behaviour in python
  6. How does Python referencing work?
  7. find all possible combinations of letters in a string in python [duplicate]
  8. Python list contents error [duplicate]
  9. How to understand regular expression with python?
  10. How to install packages offline?
  11. What is the EAFP principle in Python?
  12. Why is this printing ‘None’ in the output? [duplicate]
  13. How to make a Tkinter window jump to the front?
  14. creating spark data structure from multiline record
  15. How to extract parameters from a list and pass them to a function call [duplicate]
  16. case-insensitive list sorting, without lowercasing the result?
  17. background function in Python
  18. Capturing group with findall?
  19. How do I access Class member variables in Python?
  20. Removing all non-numeric characters from string in Python
  21. When using asyncio, how do you allow all running tasks to finish before shutting down the event loop
  22. Multiple (asynchronous) connections with urllib2 or other http library?
  23. How can I clamp (clip, restrict) a number to some range?
  24. Generating HTML documents in python
  25. Selenium can’t open a second page
  26. Python: List creation by multiplication operator time complexity
  27. Sorting a python array/recarray by column
  28. Why is numpy native on M1 Max greatly slower than on old Intel i5?
  29. How to use the __import__ function to import a name from a submodule?
  30. urllib2 and json

Leave a Comment