👻 Check our latest review to choose the best laptop for Machine Learning engineers and Deep learning tasks!
Take the following data-frame:
x = np.tile(np.arange(3),3)
y = np.repeat(np.arange(3),3)
df = pd.DataFrame({"x": x, "y": y})
x y
0 0 0
1 1 0
2 2 0
3 0 1
4 1 1
5 2 1
6 0 2
7 1 2
8 2 2
I need to sort it by x first, and only second by y:
df2 = df.sort(["x", "y"]) x y
0 0 0
3 0 1
6 0 2
1 1 0
4 1 1
7 1 2
2 2 0
5 2 1
8 2 2
How can I change the index such that it is ascending again. I.e. how do I get this:
x y
0 0 0
1 0 1
2 0 2
3 1 0
4 1 1
5 1 2
6 2 0
7 2 1
8 2 2
I have tried the following. Unfortunately, it doesn"t change the index at all:
df2.reindex(np.arange(len(df2.index)))
👻 Read also: what is the best laptop for engineering students?
Update index after sorting data-frame repeat: Questions
Create list of single item repeated N times
5 answers
I want to create a series of lists, all of varying lengths. Each list will contain the same element e, repeated n times (where n = length of the list).
How do I create the lists, without using a list comprehension [e for number in xrange(n)] for each list?
Answer #1
You can also write:
[e] * n
You should note that if e is for example an empty list you get a list with n references to the same list, not n independent empty lists.
Performance testing
At first glance it seems that repeat is the fastest way to create a list with n identical elements:
>>> timeit.timeit("itertools.repeat(0, 10)", "import itertools", number = 1000000)
0.37095273281943264
>>> timeit.timeit("[0] * 10", "import itertools", number = 1000000)
0.5577236771712819
But wait - it"s not a fair test...
>>> itertools.repeat(0, 10)
repeat(0, 10) # Not a list!!!
The function itertools.repeat doesn"t actually create the list, it just creates an object that can be used to create a list if you wish! Let"s try that again, but converting to a list:
>>> timeit.timeit("list(itertools.repeat(0, 10))", "import itertools", number = 1000000)
1.7508119747063233
So if you want a list, use [e] * n. If you want to generate the elements lazily, use repeat.
Update index after sorting data-frame repeat: Questions
What is the best way to repeatedly execute a function every x seconds?
5 answers
I want to repeatedly execute a function in Python every 60 seconds forever (just like an NSTimer in Objective C). This code will run as a daemon and is effectively like calling the python script every minute using a cron, but without requiring that to be set up by the user.
In this question about a cron implemented in Python, the solution appears to effectively just sleep() for x seconds. I don"t need such advanced functionality so perhaps something like this would work
while True:
# Code executed here
time.sleep(60)
Are there any foreseeable problems with this code?
Answer #1
If your program doesn"t have a event loop already, use the sched module, which implements a general purpose event scheduler.
import sched, time
s = sched.scheduler(time.time, time.sleep)
def do_something(sc):
print("Doing stuff...")
# do your stuff
s.enter(60, 1, do_something, (sc,))
s.enter(60, 1, do_something, (s,))
s.run()
If you"re already using an event loop library like asyncio, trio, tkinter, PyQt5, gobject, kivy, and many others - just schedule the task using your existing event loop library"s methods, instead.
Answer #2
Lock your time loop to the system clock like this:
import time
starttime = time.time()
while True:
print "tick"
time.sleep(60.0 - ((time.time() - starttime) % 60.0))
We hope this article has helped you to resolve the problem. Apart from Update index after sorting data-frame, check other repeat-related topics.
Want to excel in Python? See our review of the best Python online courses 2022. If you are interested in Data Science, check also how to learn programming in R.
By the way, this material is also available in other languages:
- Italiano Update index after sorting data-frame
- Deutsch Update index after sorting data-frame
- Français Update index after sorting data-frame
- Español Update index after sorting data-frame
- Türk Update index after sorting data-frame
- Русский Update index after sorting data-frame
- Português Update index after sorting data-frame
- Polski Update index after sorting data-frame
- Nederlandse Update index after sorting data-frame
- 中文 Update index after sorting data-frame
- 한국어 Update index after sorting data-frame
- 日本語 Update index after sorting data-frame
- हिन्दी Update index after sorting data-frame
Prague | 2022-11-28
Simply put and clear. Thank you for sharing. Update index after sorting data-frame and other issues with tile was always my weak point 😁. Will get back tomorrow with feedback
Singapore | 2022-11-28
Simply put and clear. Thank you for sharing. Update index after sorting data-frame and other issues with StackOverflow was always my weak point 😁. Checked yesterday, it works!
London | 2022-11-28
StackOverflow is always a bit confusing 😭 Update index after sorting data-frame is not the only problem I encountered. Will get back tomorrow with feedback
