Lambda in a loop [duplicate]

by

You need to bind d for each function created. One way to do that is to pass it as a parameter with a default value:

lambda d=d: self.root.change_directory(d)

Now the d inside the function uses the parameter, even though it has the same name, and the default value for that is evaluated when the function is created. To help you see this:

lambda bound_d=d: self.root.change_directory(bound_d)

Remember how default values work, such as for mutable objects like lists and dicts, because you are binding an object.

This idiom of parameters with default values is common enough, but may fail if you introspect function parameters and determine what to do based on their presence. You can avoid the parameter with another closure:

(lambda d=d: lambda: self.root.change_directory(d))()
# or
(lambda d: lambda: self.root.change_directory(d))(d)

More Related Contents:

  1. Can someone explain what all the codes mean? PYTHON [closed]
  2. look through a very large numbers (1.2e+34) in Python
  3. Create a list of names whose height is higher than 160 – Explanation on nested dicts cycling [closed]
  4. Faster version of ‘pygame.event.get()’. Why are events being missed and why are the events delayed?
  5. How do you create different variable names while in a loop? [duplicate]
  6. What is the difference between range and xrange functions in Python 2.X?
  7. raw_input and timeout [duplicate]
  8. How do I count occurrence of unique values inside a list
  9. How to add an integer to each element in a list?
  10. Python: How to keep repeating a program until a specific input is obtained? [duplicate]
  11. How to iterate over a list in chunks
  12. What is the difference between i = i + 1 and i += 1 in a ‘for’ loop? [duplicate]
  13. Skip multiple iterations in loop
  14. How do I loop through a list by twos? [duplicate]
  15. Assigning values to variables in a list using a loop
  16. python: restarting a loop
  17. Updating value in iterrow for pandas
  18. Converting for loops to while loops in python
  19. Python nested looping Idiom
  20. Understanding for loops in Python
  21. How to increment variable names/Is this a bad idea [duplicate]
  22. Why doesn’t assigning to the loop variable modify the original list? How can I assign back to the list in a loop? [duplicate]
  23. Spark iteration time increasing exponentially when using join
  24. Is there a “do … until” in Python? [duplicate]
  25. Updating a value in a pandas dataframe in an iterrows loop
  26. Iterating through a JSON object
  27. Why do you have to call .items() when iterating over a dictionary in Python?
  28. Iterating over a 2 dimensional python list [duplicate]
  29. How do I iterate over the tuples of the items of two or more lists in Python? [duplicate]
  30. Modifying a list while iterating when programming with python [duplicate]

Leave a Comment