Update value of a nested dictionary of varying depth

by

@FM’s answer has the right general idea, i.e. a recursive solution, but somewhat peculiar coding and at least one bug. I’d recommend, instead:

Python 2:

import collections

def update(d, u):
    for k, v in u.iteritems():
        if isinstance(v, collections.Mapping):
            d[k] = update(d.get(k, {}), v)
        else:
            d[k] = v
    return d

Python 3:

import collections.abc

def update(d, u):
    for k, v in u.items():
        if isinstance(v, collections.abc.Mapping):
            d[k] = update(d.get(k, {}), v)
        else:
            d[k] = v
    return d

The bug shows up when the “update” has a k, v item where v is a dict and k is not originally a key in the dictionary being updated — @FM’s code “skips” this part of the update (because it performs it on an empty new dict which isn’t saved or returned anywhere, just lost when the recursive call returns).

My other changes are minor: there is no reason for the if/else construct when .get does the same job faster and cleaner, and isinstance is best applied to abstract base classes (not concrete ones) for generality.

More Related Contents:

  1. How to end a python program without it going to the next line of code [duplicate]
  2. Unable to use convert strings into integers for a for loop
  3. Why does my recursive function return None?
  4. selenium.common.exceptions.WebDriverException: Message: ‘chromedriver’ executable needs to be in PATH error with Headless Chrome
  5. How to search for a string in text files?
  6. Why is my pygame application loop not working properly? [duplicate]
  7. How to create a trie in Python
  8. Pandas read_sql with parameters
  9. How do I find the time difference between two datetime objects in python?
  10. How to round a floating point number up to a certain decimal place?
  11. How include static files to setuptools – python package
  12. When should I subclass EnumMeta instead of Enum?
  13. Converting “yield from” statement to Python 2.7 code
  14. How can I convert 24 hour time to 12 hour time?
  15. Image comparison algorithm
  16. Proper way to feed time-series data to stateful LSTM?
  17. Python Global Variable not updating
  18. Undetected Chromedriver not loading correctly
  19. Writing to a particular cell using csv module in python
  20. How to use jinja2 as a templating engine in Django 1.8
  21. SQLAlchemy Joinedload filter column
  22. PIL “IOError: image file truncated” with big images
  23. What is the recommended way to break a long if statement? (W504 line break after binary operator)
  24. How do I use different Python version in venv from standard library? (Not virtualenv!)
  25. How do I customize the display of edge labels in networkx?
  26. Run an infinite loop in the backgroung in Tkinter
  27. what is the codec for mp4 videos in python OpenCV
  28. Python – Trap all signals
  29. What’s the best way to generate random strings of a specific length in Python?
  30. Embedding python in multithreaded C application

Leave a Comment