Is there a way to have
statements = [statement1, statement2, statement3, ...]
in Python?
I want to be able to do:
run statements[i]
or:
f = statements[j] (where f is a function)
P.S. I want to have a list of assignment statements (lambda would not work) and I rather not create functions. For example:
switch = [output = input, output = 2 * input, output = input ** 2]
Is there any other way than defining a function for each entry?
Thank you everyone who answered my question.
Yes. Functions are first-class-citizens in python: i.e. you could pass them as parameters or even store them in an array.
It is not uncommon to have a list of functions: You could build a simple registry in python like this:
#!/usr/bin/env python
processing_pipeline = []
def step(function):
processing_pipeline.append(function);
return function
@step
def step_1(data):
print("processing step1")
@step
def step_2(data):
print("processing step2")
@step
def step_3(data):
print("processing step3")
def main():
data = {}
for process in processing_pipeline:
process(data)
if __name__ == '__main__':
main()
Here the processing_pipeline is just a list with functions.
step is a so called decorator-function, which works like a closure.
The python interpreter adds while parsing the file every decorated @step to the pipeline.
And you are able to access the function with an iterator, or via processing_pipeline[i]: try adding processing_pipeline[2](data).
I want to be able to do:
run statements[i]
well, you can do that by exec:
statements = ["result=max(1,2)","print(result)"]
for idx in range(len(statements)):
exec(statements[idx])
print(result)
Hope it helps!
This is perfectly fine:
def addbla(item):
return item + ' bla'
items = ['Trump', 'Donald', 'tax declaration']
new_items = [addbla(item) for item in items]
print(new_items)
It adds a political statement to every item in items :)
If you want to run a block of statements, use a function.
def run_statements():
func()
for i in range(3):
if i > 1:
break
extra_func()
run_statements()
If you want to choose specific statements from a list, wrap each one in a function:
def looper():
for i in range(3):
if i>1:
break
def func():
print('hello')
statements = [looper, func]
statements[-1]()
If your statements are simply function calls, you can put them directly into a list without creating wrapper functions.
You can do:
funcs = [min, max, sum]
f = funcs[0]
funcs[1](1,2,3) # out 3
funcs[2]([1,2,3]) # out 6
Since we've had every other way, I thought I'd toss this out:
def a(input):
return pow(input, 3)
def b(input):
return abs(input)
def c(input):
return "I have {0} chickens".format(str(input))
#make an array of functions
foo = [a,b,c]
#make a list comprehension of the list of functions
dop = [x(3) for x in foo]
print dop
statement1 ... statementnin advance (def statement1():...or use lambdas.