Why isn”t my Pandas “apply” function referencing multiple columns working?

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I have some problems with the Pandas apply function, when using multiple columns with the following dataframe

df = DataFrame ({"a" : np.random.randn(6),
                 "b" : ["foo", "bar"] * 3,
                 "c" : np.random.randn(6)})

and the following function

def my_test(a, b):
    return a % b

When I try to apply this function with :

df["Value"] = df.apply(lambda row: my_test(row[a], row[c]), axis=1)

I get the error message:

NameError: ("global name "a" is not defined", u"occurred at index 0")

I do not understand this message, I defined the name properly.

I would highly appreciate any help on this issue

Update

Thanks for your help. I made indeed some syntax mistakes with the code, the index should be put "". However I still get the same issue using a more complex function such as:

def my_test(a):
    cum_diff = 0
    for ix in df.index():
        cum_diff = cum_diff + (a - df["a"][ix])
    return cum_diff 

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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: 
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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?

334

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

Why isn"t my Pandas "apply" function referencing multiple columns working? iat: Questions

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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:
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      modul = sys.modules[module_name]
      instance = modul.class_name() # obviously this doesn"t works, here is my main problem!
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some-dynamically-loaded-module script:

class myName:
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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...

222

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_()

Why isn"t my Pandas "apply" function referencing multiple columns working? iat: Questions

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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).

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Answer #1

import os
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