This question already has answers here:
How do I create variable variables?
(17 answers)
Closed 3 years ago.
I'm porting some Python 2 code to Python 3
I know this code snippet is bad practice, but I am looking for a way replace the exec() calls. I basically get "None" back, as predicted by the migration documents. I tried eval() but I get syntax error messages.
What are the alternatives dynamically generating variable names?
value = "test"
for field in ['overviewSynopsis', 'callsToAction_productLevel']:
exec(field +'_value = ""')
exec(field +'_value = value')
print(exec(field + "_value"))
Use a dictionary instead. You can map a key name to a value.
Related
This question already has answers here:
What does "list comprehension" and similar mean? How does it work and how can I use it?
(5 answers)
Closed 1 year ago.
I don't know Python super well but I know it well enough that I'm trying to translate some Python code to Lua. But I can't figure out what this code is supposed to do.
var_declarations = [
VarDecl(var_node, type_node)
for var_node in var_nodes
]
VarDecl is a class, and var_nodes is a list. Full code is here.
That's called a "list comprehension". It is exactly the same as:
var_declarations = []
for var_node in var_nodes:
var_declarations.append( VarDecl(var_node, type_node) )
It just builds a new list with the result of calling VarDecl one at a time.
This is a list comprehension syntax. Looking at the code snippet that you referred to, it is instantiating the VarDecl class for each var_node in var_nodes list(array) and creating a new list called var_declarations.
This question already has answers here:
How do I create variable variables?
(17 answers)
Closed 2 years ago.
I want to make a variable that can be changed iterably through for loops, as in:
for i in range(15):
var + i = 12
so that when it is finished, there will be 15 variables that has the number 12. I've done this through code.org (I'm taking computer science) and I want to know if this is possible through python.
Like that?
g = globals()
for i in range(15):
g[f'var{i}'] = 12
It can be useful for practise, to understand how variables storing. In real projects you should use some sort of collections. Usually list or dict.
This question already has answers here:
Why dict.get(key) instead of dict[key]?
(14 answers)
Closed 3 years ago.
monthConversions={
"Jan":"January", #key:value
"Feb":'February', #make sure keys are unique
'Mar':'March', #can also use integers
'Apr':"April",
'May':'May',
'Jun':'June',
}
print(monthConversions['Jan']) #gives value associated with the key
print(monthConversions.get('Luv','not a valid key'))
Hi, I am currently learning python through freebootcamp on youtube, and the person mentioned we can use the get function to pass in a value for a key that is not in the dictionary. I kind of understand that, but I fail to see what the use of this would be. I thought it would add Luv in when I put in
print(monthConversions['Luv'])
but it instead gives a error. What would be the purpose of the get function in this situation anyway? It feels like extra work and I don't get how it would be useful. Any explanations would be greatly appreciated, thank you.
It does not change the dict. The second argument is simply what get() returns when key is not found. If you don't specify it, it will simply return None.
This question already has answers here:
How do I create variable variables?
(17 answers)
How can I create multiple variables from a list of strings? [duplicate]
(2 answers)
generating variable names on fly in python [duplicate]
(6 answers)
Closed 3 years ago.
I have a ticker and I want to check a specific list of tickers to see if the ticker is found. If it is found, it will replace it.
The new tickers come from another data source and therefore do not know which specific list of tickers to check. In order to find that list, I can pass the lists name as a string but upon iterating the code (naturally) recognizes this as string as opposed to a list to iterate.
Is there a way to have the code/function recognize that the string is actually a specific list to be checked? In reading other questions, I know this may not be possible...in that case what is an alternative?
list_1=['A','B']
list_2=['C','D']
old_ticker='A'
new_ticker='E'
assigned_list='list_1'
def replace_ticker(old_ticker,new_ticker,list):
for ticker in list:
if new_ticker in list:
return
else:
list.append(new_ticker)
list.remove(old_ticker)
replace_ticker(old_ticker,new_ticker,assigned_list)
You key the needed lists by name in a dictionary:
ticker_directory = {
"list_1": list_1,
"list_2": list_2
}
Now you can accept the name and get the desired list as ticker_directory[assigned_list].
list_1=['A','B']
list_2=['C','D']
lists = {
'list_1':list_1,
'list_2':list_2
}
old_ticker='A'
new_ticker='E'
assigned_list='list_1'
def replace_ticker(old_ticker,new_ticker,list_name):
if old_ticker not in lists[list_name]:
return
else:
lists[list_name].append(new_ticker)
lists[list_name].remove(old_ticker)
replace_ticker(old_ticker,new_ticker,assigned_list)
print(lists[assigned_list])
This is the complete program from what i perceived.
#prune already answered this, I have just given the whole solution
There are at least two possibilities:
1 As noted in comments kind of overkill but possible:
Use eval() to evaluate string as python expressions more in the link:
https://thepythonguru.com/python-builtin-functions/eval/
For example:
list_name = 'list_1'
eval('{}.append(new_ticker)'.format(list_name))
2 Second
Using locals() a dictionary of locally scoped variables similiar to the other answers but without the need of creating the dict by hand which also requires the knowledge of all variables names.
list_name = 'list_1'
locals()[list_name].append(new_ticker)
This question already has answers here:
Python Argument Binders
(7 answers)
Closed 8 months ago.
As you can see from the code below, I'm adding a series of functions to a list.
The result is that each function gets ran and the returned value is added to the list.
foo_list = []
foo_list.append(bar.func1(100))
foo_list.append(bar.func2([7,7,7,9]))
foo_list.append(bar.func3(r'C:\Users\user\desktop\output'))
What I would like to know is, is it possible to have the function stored in the list and then ran when it is iterated upon in a for loop?
Yeah just use lambda:
foo_list = []
foo_list.append(lambda: bar.func1(100))
foo_list.append(lambda: bar.func2([7,7,7,9]))
foo_list.append(lambda: bar.func3(r'C:\Users\user\desktop\output'))
for foo in foo_list:
print(foo())