How to "Test" Nonetype in Python

How to test NoneType in python?

So how can I question a variable that is a NoneType?

Use is operator, like this

if variable is None:

Why this works?

Since None is the sole singleton object of NoneType in Python, we can use is operator to check if a variable has None in it or not.

Quoting from is docs,

The operators is and is not test for object identity: x is y is true if and only if x and y are the same object. x is not y yields the inverse truth value.

Since there can be only one instance of None, is would be the preferred way to check None.

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Hear it from the horse's mouth

Quoting Python's Coding Style Guidelines - PEP-008 (jointly defined by Guido himself),

Comparisons to singletons like None should always be done with is or is not, never the equality operators.

Determining a variable's type is NoneType in python

NoneType just happens to not automatically be in the global scope. This isn't really a problem.

>>> NoneType = type(None)
>>> x = None
>>> type(x) == NoneType
True
>>> isinstance(x, NoneType)
True

In any case it would be unusual to do a type check. Rather you should test x is None.

What is a 'NoneType' object?

NoneType is the type for the None object, which is an object that indicates no value. None is the return value of functions that "don't return anything". It is also a common default return value for functions that search for something and may or may not find it; for example, it's returned by re.search when the regex doesn't match, or dict.get when the key has no entry in the dict. You cannot add None to strings or other objects.

One of your variables is None, not a string. Maybe you forgot to return in one of your functions, or maybe the user didn't provide a command-line option and optparse gave you None for that option's value. When you try to add None to a string, you get that exception:

send_command(child, SNMPGROUPCMD + group + V3PRIVCMD)

One of group or SNMPGROUPCMD or V3PRIVCMD has None as its value.

not None test in Python

if val is not None:
    # ...

is the Pythonic idiom for testing that a variable is not set to None. This idiom has particular uses in the case of declaring keyword functions with default parameters. is tests identity in Python. Because there is one and only one instance of None present in a running Python script/program, is is the optimal test for this. As Johnsyweb points out, this is discussed in PEP 8 under "Programming Recommendations".

As for why this is preferred to

if not (val is None):
    # ...

this is simply part of the Zen of Python: "Readability counts." Good Python is often close to good pseudocode.

Python3 cant detectclass 'NoneType'

fieldType is <class 'NoneType'>, which is different from None. It can never be None, because type always returns some type.

Looks like you want

raw_data[root_key].get("oslc_cm:ChangeRequest") is None

instead of

fieldType is None

Testing Nonetype elements in a list

all() tells you if every element in the iterable you pass to it is True. So, all([True, True, True]) would be True, but all([True, False]) wouldn't.

If you want to see if all elements are None, this is what you need:

all(x is None for x in inputs)

What this does is use a generator to loop over all the values in inputs, checking if they are None and all() checks all those results and returns True if all of them are True.

NoneType' object has no attribute 'text', beautifulsoup python

Some list of items may not have price value.So you might use try except and also need to add user-agent . It always be better practice not using list as variable as list is a python keyword. Now it's working smoothly.

from bs4 import BeautifulSoup
import requests
import csv

csv_file = open('CultBeauty.csv', 'w', encoding='utf-8')
csv_writer = csv.writer(csv_file)
csv_writer.writerow(['Product Name', 'Price'])
headers={"User-Agent":"mozilla/5.0"}
for i in range(10):
    url = requests.get('https://www.cultbeauty.com/skin-care.list?pageNumber={}&facetFilters=en_beauty_skincareSkinType_content:Dry'.format(i+1),headers=headers).text
    soup = BeautifulSoup(url, 'lxml')
    lists = soup.find_all('div', class_="productBlock")
    for lis in lists:
        ProductName = lis.find('h3', class_="productBlock_productName")
        ProductName = ProductName.text.strip()
        print(ProductName)
        try:
            Price = lis.find('span', {'class': "productBlock_priceValue"})
            Price = Price.text.strip()
            print(Price)
        except:
            pass
        csv_writer.writerow([ProductName, Price])
csv_file.close()

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