I"m new to pandas and trying to figure out how to add multiple columns to pandas simultaneously. Any help here is appreciated. Ideally I would like to do this in one step rather than multiple repeated steps...
import pandas as pd
df = {"col_1": [0, 1, 2, 3],
"col_2": [4, 5, 6, 7]}
df = pd.DataFrame(df)
df[[ "column_new_1", "column_new_2","column_new_3"]] = [np.nan, "dogs",3] #thought this would work here...
How to add multiple columns to pandas dataframe in one assignment? iat: Questions
InsecurePlatformWarning: A true SSLContext object is not available. This prevents urllib3 from configuring SSL appropriately
3 answers
Tried to perform REST GET through python requests with the following code and I got error.
Code snip:
import requests
header = {"Authorization": "Bearer..."}
url = az_base_url + az_subscription_id + "/resourcegroups/Default-Networking/resources?" + az_api_version
r = requests.get(url, headers=header)
Error:
/usr/local/lib/python2.7/dist-packages/requests/packages/urllib3/util/ssl_.py:79:
InsecurePlatformWarning: A true SSLContext object is not available.
This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail.
For more information, see https://urllib3.readthedocs.org/en/latest/security.html#insecureplatformwarning.
InsecurePlatformWarning
My python version is 2.7.3. I tried to install urllib3 and requests[security] as some other thread suggests, I still got the same error.
Wonder if anyone can provide some tips?
Answer #1
The docs give a fair indicator of what"s required., however requests allow us to skip a few steps:
You only need to install the security package extras (thanks @admdrew for pointing it out)
$ pip install requests[security]
or, install them directly:
$ pip install pyopenssl ndg-httpsclient pyasn1
Requests will then automatically inject pyopenssl into urllib3
If you"re on ubuntu, you may run into trouble installing pyopenssl, you"ll need these dependencies:
$ apt-get install libffi-dev libssl-dev
Dynamic instantiation from string name of a class in dynamically imported module?
3 answers
In python, I have to instantiate certain class, knowing its name in a string, but this class "lives" in a dynamically imported module. An example follows:
loader-class script:
import sys
class loader:
def __init__(self, module_name, class_name): # both args are strings
try:
__import__(module_name)
modul = sys.modules[module_name]
instance = modul.class_name() # obviously this doesn"t works, here is my main problem!
except ImportError:
# manage import error
some-dynamically-loaded-module script:
class myName:
# etc...
I use this arrangement to make any dynamically-loaded-module to be used by the loader-class following certain predefined behaviours in the dyn-loaded-modules...
Answer #1
You can use getattr
getattr(module, class_name)
to access the class. More complete code:
module = __import__(module_name)
class_ = getattr(module, class_name)
instance = class_()
As mentioned below, we may use importlib
import importlib
module = importlib.import_module(module_name)
class_ = getattr(module, class_name)
instance = class_()
How to get all of the immediate subdirectories in Python
3 answers
I"m trying to write a simple Python script that will copy a index.tpl to index.html in all of the subdirectories (with a few exceptions).
I"m getting bogged down by trying to get the list of subdirectories.
Answer #1
import os
def get_immediate_subdirectories(a_dir):
return [name for name in os.listdir(a_dir)
if os.path.isdir(os.path.join(a_dir, name))]
How to add multiple columns to pandas dataframe in one assignment? 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.
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))
