You can use dir(module) to see all available methods/attributes. Also check out PyDocs.
Is there a list of every Python function out there?
How do Python's any and all functions work? - Stack Overflow
How does the "all" function in Python work? - Stack Overflow
How all() function actually works?
Videos
You can use dir(module) to see all available methods/attributes. Also check out PyDocs.
Use the inspect module:
from inspect import getmembers, isfunction
from somemodule import foo
print(getmembers(foo, isfunction))
Also see the pydoc module, the help() function in the interactive interpreter and the pydoc command-line tool which generates the documentation you are after. You can just give them the class you wish to see the documentation of. They can also generate, for instance, HTML output and write it to disk.
I recently learnt that stuff like .strip(), .title(), exists, which got me interested to learn about all these little bonus gimmicks about Python that I could use in my everyday tasks or to improve functionality in my code.
As of now I know that https://docs.python.org/3/library/functions.html exists but there isn't the functions mentioned above within that list. Is there another list of all these functions including those mentioned out there? Thank you
You can roughly think of any and all as series of logical or and and operators, respectively.
any
any will return True when at least one of the elements is Truthy. Read about Truth Value Testing.
all
all will return True only when all the elements are Truthy.
Truth table
+-----------------------------------------+---------+---------+
| | any | all |
+-----------------------------------------+---------+---------+
| All Truthy values | True | True |
+-----------------------------------------+---------+---------+
| All Falsy values | False | False |
+-----------------------------------------+---------+---------+
| One Truthy value (all others are Falsy) | True | False |
+-----------------------------------------+---------+---------+
| One Falsy value (all others are Truthy) | True | False |
+-----------------------------------------+---------+---------+
| Empty Iterable | False | True |
+-----------------------------------------+---------+---------+
Note 1: The empty iterable case is explained in the official documentation, like this
any
Return
Trueif any element of the iterable is true. If the iterable is empty, returnFalse
Since none of the elements are true, it returns False in this case.
all
Return
Trueif all elements of the iterable are true (or if the iterable is empty).
Since none of the elements are false, it returns True in this case.
Note 2:
Another important thing to know about any and all is, it will short-circuit the execution, the moment they know the result. The advantage is, entire iterable need not be consumed. For example,
>>> multiples_of_6 = (not (i % 6) for i in range(1, 10))
>>> any(multiples_of_6)
True
>>> list(multiples_of_6)
[False, False, False]
Here, (not (i % 6) for i in range(1, 10)) is a generator expression which returns True if the current number within 1 and 9 is a multiple of 6. any iterates the multiples_of_6 and when it meets 6, it finds a Truthy value, so it immediately returns True, and rest of the multiples_of_6 is not iterated. That is what we see when we print list(multiples_of_6), the result of 7, 8 and 9.
This excellent thing is used very cleverly in this answer.
With this basic understanding, if we look at your code, you do
any(x) and not all(x)
which makes sure that, atleast one of the values is Truthy but not all of them. That is why it is returning [False, False, False]. If you really wanted to check if both the numbers are not the same,
print [x[0] != x[1] for x in zip(*d['Drd2'])]
How do Python's
anyandallfunctions work?
any and all take iterables and return True if any and all (respectively) of the elements are True.
>>> any([0, 0.0, False, (), '0']), all([1, 0.0001, True, (False,)])
(True, True) # ^^^-- truthy non-empty string
>>> any([0, 0.0, False, (), '']), all([1, 0.0001, True, (False,), {}])
(False, False) # ^^-- falsey
If the iterables are empty, any returns False, and all returns True.
>>> any([]), all([])
(False, True)
I was demonstrating all and any for students in class today. They were mostly confused about the return values for empty iterables. Explaining it this way caused a lot of lightbulbs to turn on.
Shortcutting behavior
They, any and all, both look for a condition that allows them to stop evaluating. The first examples I gave required them to evaluate the boolean for each element in the entire list.
(Note that list literal is not itself lazily evaluated - you could get that with an Iterator - but this is just for illustrative purposes.)
Here's a Python implementation of any and all:
def any(iterable):
for i in iterable:
if i:
return True
return False # for an empty iterable, any returns False!
def all(iterable):
for i in iterable:
if not i:
return False
return True # for an empty iterable, all returns True!
Of course, the real implementations are written in C and are much more performant, but you could substitute the above and get the same results for the code in this (or any other) answer.
all
all checks for elements to be False (so it can return False), then it returns True if none of them were False.
>>> all([1, 2, 3, 4]) # has to test to the end!
True
>>> all([0, 1, 2, 3, 4]) # 0 is False in a boolean context!
False # ^--stops here!
>>> all([])
True # gets to end, so True!
any
The way any works is that it checks for elements to be True (so it can return True), then it returnsFalseif none of them wereTrue`.
>>> any([0, 0.0, '', (), [], {}]) # has to test to the end!
False
>>> any([1, 0, 0.0, '', (), [], {}]) # 1 is True in a boolean context!
True # ^--stops here!
>>> any([])
False # gets to end, so False!
I think if you keep in mind the short-cutting behavior, you will intuitively understand how they work without having to reference a Truth Table.
Evidence of all and any shortcutting:
First, create a noisy_iterator:
def noisy_iterator(iterable):
for i in iterable:
print('yielding ' + repr(i))
yield i
and now let's just iterate over the lists noisily, using our examples:
>>> all(noisy_iterator([1, 2, 3, 4]))
yielding 1
yielding 2
yielding 3
yielding 4
True
>>> all(noisy_iterator([0, 1, 2, 3, 4]))
yielding 0
False
We can see all stops on the first False boolean check.
And any stops on the first True boolean check:
>>> any(noisy_iterator([0, 0.0, '', (), [], {}]))
yielding 0
yielding 0.0
yielding ''
yielding ()
yielding []
yielding {}
False
>>> any(noisy_iterator([1, 0, 0.0, '', (), [], {}]))
yielding 1
True
The source
Let's look at the source to confirm the above.
Here's the source for any:
static PyObject *
builtin_any(PyObject *module, PyObject *iterable)
{
PyObject *it, *item;
PyObject *(*iternext)(PyObject *);
int cmp;
it = PyObject_GetIter(iterable);
if (it == NULL)
return NULL;
iternext = *Py_TYPE(it)->tp_iternext;
for (;;) {
item = iternext(it);
if (item == NULL)
break;
cmp = PyObject_IsTrue(item);
Py_DECREF(item);
if (cmp < 0) {
Py_DECREF(it);
return NULL;
}
if (cmp > 0) {
Py_DECREF(it);
Py_RETURN_TRUE;
}
}
Py_DECREF(it);
if (PyErr_Occurred()) {
if (PyErr_ExceptionMatches(PyExc_StopIteration))
PyErr_Clear();
else
return NULL;
}
Py_RETURN_FALSE;
}
And here's the source for all:
static PyObject *
builtin_all(PyObject *module, PyObject *iterable)
{
PyObject *it, *item;
PyObject *(*iternext)(PyObject *);
int cmp;
it = PyObject_GetIter(iterable);
if (it == NULL)
return NULL;
iternext = *Py_TYPE(it)->tp_iternext;
for (;;) {
item = iternext(it);
if (item == NULL)
break;
cmp = PyObject_IsTrue(item);
Py_DECREF(item);
if (cmp < 0) {
Py_DECREF(it);
return NULL;
}
if (cmp == 0) {
Py_DECREF(it);
Py_RETURN_FALSE;
}
}
Py_DECREF(it);
if (PyErr_Occurred()) {
if (PyErr_ExceptionMatches(PyExc_StopIteration))
PyErr_Clear();
else
return NULL;
}
Py_RETURN_TRUE;
}
only when all the elements are Truthy.
Truthy != True.
all essentially checks whether bool(something) is True (for all somethings in the iterable).
>>> "?" == True
False
>>> "?" == False # it's not False either
False
>>> bool("?")
True
'?' and '!' are both truthy since they are non-empty Strings.
There's a difference between True and "truthy". Truthy means that when coerced, it can evaluate to True. That's different from it being == to True though.