Develop Reference

Formatting problem from string to Datetime [duplicate]

This question already has answers here:
What is the difference between __str__ and __repr__?
(28 answers)
Closed 5 months ago.
I'm trying to parse a string with the datetime standard library module and then display it.
When I try this code, the output looks correct:
>>> import datetime
>>> endDate = datetime.datetime.strptime("2022-05-03", '%Y-%m-%d').date()
>>> print(endDate)
2022-05-03
But it changes if the endDate is put into a list or tuple:
>>> print([endDate])
[datetime.date(2022, 5, 3)]
Why does the output have the "datetime.date" text?

>>> from datetime import datetime
>>> endDate = datetime.strptime("2022-05-03", '%Y-%m-%d').date()
When you printed the date object, it used str representation of the date object.
>>> str(endDate)
'2022-05-03'
When you included that in a container and printed it, the container internally uses repr representation of the object
>>> repr(endDate)
'datetime.date(2022, 5, 3)'
print function by default converts all the objects passed to it to a String with str.
All non-keyword arguments are converted to strings like str() does
To understand this better, we can create a class which implements both __str__ and __repr__ functions like this
>>> class Test:
... def __str__(self):
... return "TEST_FROM_STR"
...
... def __repr__(self):
... return "TEST_FROM_REPR"
...
Now, we can create instances of that class and print them separately and with list, like this
>>> Test()
TEST_FROM_REPR
>>> [Test()]
[TEST_FROM_REPR]
>>> print(Test())
TEST_FROM_STR
>>> print([Test()])
[TEST_FROM_REPR]

Function argument for an f-string '=' debugging operator [duplicate]

This question already has answers here:
How to get the original variable name of variable passed to a function [duplicate]
(13 answers)
Closed 1 year ago.
How to pass a variable for an f-string '=' debugging operator?
from datetime import datetime
def print_var(var):
print(str(datetime.now())[:19], end=' ')
print(f'{var = }')
test = 5
print_var(test)
I expect print_var(test) to print the variable name from outside the function, ie.
test = 5
Please refer to Python: Print a variable's name and value? for the context of the question.

In f-strings you need to put the variable that needs to be printed between accolades. Like this:
from datetime import datetime
def print_var(var):
print(str(datetime.now())[:19], end=' ')
print(f'var = {var}')
Running the test yields the following:
test = 5
print_var(test)
>>>2021-10-06 11:32:05 var = 5

How to dynamically print the arguments used in a function call? [duplicate]

This question already has answers here:
How to get the original variable name of variable passed to a function [duplicate]
(13 answers)
Closed 2 years ago.
I have the following code:
var1='aaa'
var2='bbb'
debug(var1, var2)
I would like the debug function to print:
"var1=aaa var2=bbb"
My function currently looks like
def debug(thing1, thing2):
print(f"{thing1=} {thing2=}")
and outputs:
"thing1=aaa thing2=bbb"
I tried using locals() in the function as well but got the same output. I would like to have "var1" and "var2" in the output without hardcoding them in the print statement.

You need to come at this problem in a slightly different way.
As stated, there is no way for debug to know the variable names.
You need to supply that information:
>>> import pprint
>>> var1 = 'aaa'
>>> var2 = 'bbb'
>>> def debug(**kwargs):
... pprint.pprint(kwargs, width=20)
...
>>> debug(var1=var1, var2=var2)
{'var1': 'aaa',
'var2': 'bbb'}

Do stuff with variable that has the same name of a string [duplicate]

This question already has answers here:
How to use string value as a variable name in Python? [duplicate]
(3 answers)
How do I create variable variables?
(17 answers)
Closed 4 years ago.
let's say I have a variable called "x" and a string that has the value of "x" (string1 = "x"). How do I do stuff with the variable through the string?
For example change the variable's value or call a method if it's an object?
Thanks in advance

Variables are available through dictionaries locals() and globals(). If you want to access a particular variable by it's spring name, you can do e.g.
>>> my_var = 'hello'
>>> x = 'my_var'
>>> locals()[x]
'hello'
You can also assign back to the variable using this approach, e.g.
>>> my_var = 'hello'
>>> x = 'my_var'
>>> locals()[x] = 'something else'
>>> my_var
'something else'
Since functions are objects in Python, you can access any locally available functions in the same manner to call them.
>>> def my_test_function(n):
>>> return n*8
Accessing the method and calling it.
>>> locals()['my_test_function'](4)
32
For accessing attributes of objects by their name you can use getattr(), and setattr() to set them. For example, creating an object with a single property called your_prop.
class Example:
your_prop = 2
a = Example()
The value is available via your_prop.
>>> a.your_prop
2
The property can be accessed via name using getattr
>>> getattr(a, 'your_prop')
2
The property can be set using setattr:
>>> setattr(a, 'your_prop', 5)
>>> a.your_prop
5

Ok, let's suppose that you have lots of different functions: Aoo(), Boo(), Coo()... and let's suppose that you want to specify which of them to call via command line argument.
Now, that argument will be a string, so you need to call a function through its name, but you do not know in advance the name of the function.
One possible solution is to use exec():
def boo():
print("boo function")
def coo():
print("coo function")
Now:
argument = "boo"
exec(argument + "()")
>>> boo function
and
argument = "coo"
exec(argument + "()")
>>> coo function

It depends what you're trying to do, but you can scoop up whatever x is pointing to with locals() or globals():
def x(k):
return k + 1
string1 = "x"
the_function_x = locals()[string1]
print(the_function_x(3))
outputs 4 (it called the x function by utilizing string1).

How to call a function using dictionary key Value? [duplicate]

This question already has answers here:
Is there a way to store a function in a list or dictionary so that when the index (or key) is called it fires off the stored function?
(3 answers)
Closed 4 years ago.
Here I am trying to call a function using dictionary key value.
>>> def hello():
print('hello')
>>> a = {'+': hello()}
it just prints hello after executing this line.
>>> a['+']
If I call the dictionary using key value, it results nothing. What am I missing here?

Do not put () while you are using the function name as a value for the dictionary because as soon as python find () it will execute the function.
Instead just add the function name a = {'+': hello}
And then use the () while fetching the value from the dictionary
a["+"]()

You need a return call.
def hello():
return 'hello'
Or I think that is what you want

You should put your callable as the value into the dict and then call it.
>>> def hello():
print('hello')
>>> a = {'+': hello}
>>> a['+']()
hello