The statement
if A:
will call A.__nonzero__()
(see Special method names documentation) and use the return value of that function. Here’s the summary:
object.__nonzero__(self)
Called to implement truth value testing and the built-in operation bool()
; should return False
or True
, or their integer equivalents 0
or 1
. When this method is not defined, __len__()
is called, if it is defined, and the object is considered true if its result is nonzero. If a class defines neither __len__()
nor __nonzero__()
, all its instances are considered true.
On the other hand,
if A is not None:
compares only the reference A
with None
to see whether it is the same or not.
Related Posts:
- Pig Latin Translator
- Understanding slice notation
- How do you round UP a number?
- How to open a file using the open with statement
- How to comment out a block of code in Python [duplicate]
- Using “with open() as file” method, how to write more than once? [duplicate]
- How do I get a substring of a string in Python?
- strip(char) on a string
- How can I represent an infinite number in Python?
- Constructing pandas DataFrame from values in variables gives “ValueError: If using all scalar values, you must pass an index”
- TypeError: ‘NoneType’ object is not iterable in Python
- Relative imports – ModuleNotFoundError: No module named x
- ValueError: invalid literal for int() with base 10: ”
- What does the “yield” keyword do?
- How do I get the number of elements in a list?
- How do I list all files of a directory?
- How to copy a dictionary and only edit the copy
- Creating a static class with no instances
- How to avoid “RuntimeError: dictionary changed size during iteration” error?
- if/else in a list comprehension
- Could not find a version that satisfies the requirement tensorflow
- Creating an empty Pandas DataFrame, then filling it?
- Finding the average of a list
- How to solve dictionary changed size during iteration error?
- iloc giving ‘IndexError: single positional indexer is out-of-bounds’
- What does “\r” do in the following script?
- Anaconda vs. miniconda
- No module named serial
- ImportError: No module named psycopg2
- DataFrame constructor not properly called
- How does functools partial do what it does?
- What does pythonic mean?
- Python strip with \n [duplicate]
- ImportError: Missing required dependencies [‘numpy’]
- Tkinter understanding mainloop
- How can I get a list shape without using numpy?
- AttributeError: ‘str’ object has no attribute ‘append’
- python socket.error: [Errno 98] Address already in use
- How to read a .xlsx file using the pandas Library in iPython?
- Numpy/Python Array Value error
- Changing the “tick frequency” on x or y axis in matplotlib?
- TypeError: unsupported operand type(s) for -: ‘str’ and ‘str’
- Remove all special characters, punctuation and spaces from string
- AttributeError: ” object has no attribute ”
- Plot pie chart and table of pandas dataframe
- ModuleNotFoundError: No module named ‘matplotlib’
- “inconsistent use of tabs and spaces in indentation”
- Pandas ‘count(distinct)’ equivalent
- How can I flush the output of the print function?
- Python [Errno 98] Address already in use
- How do you call an instance of a class in Python?
- Flask ImportError: No Module Named Flask
- How do you use subprocess.check_output() in Python?
- ImportError: libcuda.so.1: cannot open shared object file
- TypeError: list indices must be integers or slices, not str
- python object() takes no parameters error
- How do I find the distance between two points?
- How do I calculate percentiles with python/numpy?
- How do I remove a substring from the end of a string?
- Selecting with complex criteria from pandas.DataFrame
- How can I download Anaconda for python 3.6
- django:django.core.exceptions.AppRegistryNotReady: Apps aren’t loaded yet
- Replace and overwrite instead of appending
- Pytesseract : “TesseractNotFound Error: tesseract is not installed or it’s not in your path”, how do I fix this?
- Pointers in Python?
- Django – no such table exception
- How to make a histogram from a list of data
- Using __add__ operator with multiple arguments in Python
- How to constantly run Python script in the background on Windows?
- Django – “no module named django.core.management”
- What does “Symbol not found / Expected in: flat namespace” actually mean?
- Windows path in Python
- Python: ValueError: Mixing iteration and read methods would lose data
- python: restarting a loop
- “for loop” with two variables?
- Find the unique values in a column and then sort them
- How to install discord.py rewrite?
- Python: urllib.error.HTTPError: HTTP Error 404: Not Found
- Display number with leading zeros
- Running Python in PowerShell?
- Why do many examples use `fig, ax = plt.subplots()` in Matplotlib/pyplot/python
- ImportError: No module named model_selection
- Numpy – add row to array
- How to change pip installation path
- What is the difference between a string and a byte string?
- CSV new-line character seen in unquoted field error
- Creating a truth table for any expression in Python
- Rolling or sliding window iterator?
- What is a namespace object?
- How to serve static files in Flask
- How to create Gephi network graphs from Python?
- strncmp in python
- TypeError: ManyRelatedManager object is not iterable
- vectorize conditional assignment in pandas dataframe
- Using print() (the function version) in Python2.x
- Is it possible to forward-declare a function in Python?
- Python OpenCV2 (cv2) wrapper to get image size?
- KeyError: ‘plotly_domain’
- The value of _stdout is incorrect
- Running a python script within wordpress