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How do I clone a Django model instance object and save it to the database?
...imary key of your object and run save().
obj = Foo.objects.get(pk=<some_existing_pk>)
obj.pk = None
obj.save()
If you want auto-generated key, set the new key to None.
More on UPDATE/INSERT here.
Official docs on copying model instances: https://docs.djangoproject.com/en/2.2/topics/db/que...
What happens when there's insufficient memory to throw an OutOfMemoryError?
...
The JVM never really runs out of memory. It does memory computation of the heap stack in advance.
The Structure of the JVM, Chapter 3, section 3.5.2 states:
If Java virtual machine stacks can be dynamically expanded, and expansion is...
How to write log to file
... answered Nov 13 '13 at 22:56
Allison AAllison A
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How to rollback a specific migration?
...nt to go back.
For example:
rake db:rollback STEP=5
Will also rollback all the migration that happened later (4, 3, 2 and also 1).
To roll back all migrations back to (and including) a target migration, use: (This corrected command was added AFTER all the comments pointing out the error in the ...
How do I use vim registers?
...on Windows (or from "mouse highlight" clipboard on Linux)
"*p
To access all currently defined registers type
:reg
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Sorting Python list based on the length of the string
...
def lensort(list_1):
list_2=[];list_3=[]
for i in list_1:
list_2.append([i,len(i)])
list_2.sort(key = lambda x : x[1])
for i in list_2:
list_3.append(i[0])
return list_3
This works for me!
...
How do I run a Ruby file in a Rails environment?
...------
#!/usr/bin/env /Users/me/rails_project/script/rails runner
Product.all.each { |p| p.price *= 2 ; p.save! }
-------------------------------------------------------------
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adding noise to a signal in python
...umpy as np
import matplotlib.pyplot as plt
t = np.linspace(1, 100, 1000)
x_volts = 10*np.sin(t/(2*np.pi))
plt.subplot(3,1,1)
plt.plot(t, x_volts)
plt.title('Signal')
plt.ylabel('Voltage (V)')
plt.xlabel('Time (s)')
plt.show()
x_watts = x_volts ** 2
plt.subplot(3,1,2)
plt.plot(t, x_watts)
plt.title...
Backbone.View “el” confusion
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A views el is where all the event binding takes place. You don't have to use it but if you want backbone to fire events you need to do your rendering work on the el. A views el is a DOM element but it does not have to be a pre-existing element. ...
What is memoization and how can I use it in Python?
...orials using memoization in Python would be something like this:
factorial_memo = {}
def factorial(k):
if k < 2: return 1
if k not in factorial_memo:
factorial_memo[k] = k * factorial(k-1)
return factorial_memo[k]
You can get more complicated and encapsulate the memoization...