Storing function name in dictionary and returning function name with parameters
def add(op1,op2):
return op1 + op2
def sub(op1,op2):
return op1 - op2
def mul(op1,op2):
return op1 * op2
def div(op1,op2):
return op1 / op2
def evaluate(op1,operator,op2):
ops = {'+':add,'-':sub,'*':mul,'/':div}
return ops[operator](op1,op2)
print(evaluate(1,'/',2))
>>> 0.5
I was messing around with dictionaries and I got this idea of storing a function name as a value and then returning that function name with parameters. I was surprised to see it actually worked. I don't know how this is possible and what's going on behind the scenes so can someone explain to me what exactly is happening in this piece of code in detail?
python python-3.x
asked Nov 22 '18 at 23:51
BrowserMBrowserM
214
add a comment |
def add(op1,op2):
return op1 + op2
def sub(op1,op2):
return op1 - op2
def mul(op1,op2):
return op1 * op2
def div(op1,op2):
return op1 / op2
def evaluate(op1,operator,op2):
ops = {'+':add,'-':sub,'*':mul,'/':div}
return ops[operator](op1,op2)
print(evaluate(1,'/',2))
>>> 0.5
I was messing around with dictionaries and I got this idea of storing a function name as a value and then returning that function name with parameters. I was surprised to see it actually worked. I don't know how this is possible and what's going on behind the scenes so can someone explain to me what exactly is happening in this piece of code in detail?
python python-3.x
asked Nov 22 '18 at 23:51
BrowserMBrowserM
214
1
Functions are objects. They can be assigned, stored, and passed as parameters, just like any other object.
– John Gordon
Nov 22 '18 at 23:57
add a comment |
def add(op1,op2):
return op1 + op2
def sub(op1,op2):
return op1 - op2
def mul(op1,op2):
return op1 * op2
def div(op1,op2):
return op1 / op2
def evaluate(op1,operator,op2):
ops = {'+':add,'-':sub,'*':mul,'/':div}
return ops[operator](op1,op2)
print(evaluate(1,'/',2))
>>> 0.5
I was messing around with dictionaries and I got this idea of storing a function name as a value and then returning that function name with parameters. I was surprised to see it actually worked. I don't know how this is possible and what's going on behind the scenes so can someone explain to me what exactly is happening in this piece of code in detail?
python python-3.x
asked Nov 22 '18 at 23:51
BrowserMBrowserM
214
def add(op1,op2):
return op1 + op2
def sub(op1,op2):
return op1 - op2
def mul(op1,op2):
return op1 * op2
def div(op1,op2):
return op1 / op2
def evaluate(op1,operator,op2):
ops = {'+':add,'-':sub,'*':mul,'/':div}
return ops[operator](op1,op2)
print(evaluate(1,'/',2))
>>> 0.5
I was messing around with dictionaries and I got this idea of storing a function name as a value and then returning that function name with parameters. I was surprised to see it actually worked. I don't know how this is possible and what's going on behind the scenes so can someone explain to me what exactly is happening in this piece of code in detail?
python python-3.x
python python-3.x
asked Nov 22 '18 at 23:51
BrowserMBrowserM
214
asked Nov 22 '18 at 23:51
BrowserMBrowserM
214
asked Nov 22 '18 at 23:51
BrowserMBrowserM
214
asked Nov 22 '18 at 23:51
BrowserMBrowserM
214
asked Nov 22 '18 at 23:51
BrowserMBrowserM
214
214
1
Functions are objects. They can be assigned, stored, and passed as parameters, just like any other object.
– John Gordon
Nov 22 '18 at 23:57
add a comment |
1
Functions are objects. They can be assigned, stored, and passed as parameters, just like any other object.
– John Gordon
Nov 22 '18 at 23:57
1
1
Functions are objects. They can be assigned, stored, and passed as parameters, just like any other object.
– John Gordon
Nov 22 '18 at 23:57
Functions are objects. They can be assigned, stored, and passed as parameters, just like any other object.
– John Gordon
Nov 22 '18 at 23:57
add a comment |
2 Answers
2
active
oldest
votes
If you're experienced in C or C++, then you'll be aware of the idea of "function pointers" - you take the memory address of a function, put it in a variable, and then later execute "the function at that memory address". It's pretty much the same in python.
Essentially, python treats a function as its own type of object:
>>> def x():
... print("Hello World")
...
>>> type(x)
<class 'function'>
A function can be called with the parentheses operators, obviously. However, since a function is also an object, you can put that function inside of a variable:
>>> y = x
>>> y()
Hello World
What you're doing with the dict is making key-value pairs: "+" corresponds to the object add; and since add is a function, it can be called.
answered Nov 23 '18 at 0:00
Green Cloak GuyGreen Cloak Guy
2,6181720
add a comment |
To Explain:
The first four functions are making operator functions
Then in the
evaluatefunction, it creates a dictionary, with the signs as key, and the functions as valuesThen, get the
operatorargument, which is one of the signs, so get the value of the key:value pair when the key is that sign, then you just call that value since it's a function
Note that there's a better code, actually operator module contains the first four functions already.
The code for that:
from operator import add,sub,mul,truediv
def evaluate(op1,operator,op2):
ops = {'+':add,'-':sub,'*':mul,'/':truediv}
return ops[operator](op1,op2)
print(evaluate(1,'/',2))
Output:
0.5
answered Nov 22 '18 at 23:55
U9-ForwardU9-Forward
14.8k41338
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
If you're experienced in C or C++, then you'll be aware of the idea of "function pointers" - you take the memory address of a function, put it in a variable, and then later execute "the function at that memory address". It's pretty much the same in python.
Essentially, python treats a function as its own type of object:
>>> def x():
... print("Hello World")
...
>>> type(x)
<class 'function'>
A function can be called with the parentheses operators, obviously. However, since a function is also an object, you can put that function inside of a variable:
>>> y = x
>>> y()
Hello World
What you're doing with the dict is making key-value pairs: "+" corresponds to the object add; and since add is a function, it can be called.
answered Nov 23 '18 at 0:00
Green Cloak GuyGreen Cloak Guy
2,6181720
add a comment |
If you're experienced in C or C++, then you'll be aware of the idea of "function pointers" - you take the memory address of a function, put it in a variable, and then later execute "the function at that memory address". It's pretty much the same in python.
Essentially, python treats a function as its own type of object:
>>> def x():
... print("Hello World")
...
>>> type(x)
<class 'function'>
A function can be called with the parentheses operators, obviously. However, since a function is also an object, you can put that function inside of a variable:
>>> y = x
>>> y()
Hello World
What you're doing with the dict is making key-value pairs: "+" corresponds to the object add; and since add is a function, it can be called.
answered Nov 23 '18 at 0:00
Green Cloak GuyGreen Cloak Guy
2,6181720
add a comment |
If you're experienced in C or C++, then you'll be aware of the idea of "function pointers" - you take the memory address of a function, put it in a variable, and then later execute "the function at that memory address". It's pretty much the same in python.
Essentially, python treats a function as its own type of object:
>>> def x():
... print("Hello World")
...
>>> type(x)
<class 'function'>
A function can be called with the parentheses operators, obviously. However, since a function is also an object, you can put that function inside of a variable:
>>> y = x
>>> y()
Hello World
What you're doing with the dict is making key-value pairs: "+" corresponds to the object add; and since add is a function, it can be called.
answered Nov 23 '18 at 0:00
Green Cloak GuyGreen Cloak Guy
2,6181720
If you're experienced in C or C++, then you'll be aware of the idea of "function pointers" - you take the memory address of a function, put it in a variable, and then later execute "the function at that memory address". It's pretty much the same in python.
Essentially, python treats a function as its own type of object:
>>> def x():
... print("Hello World")
...
>>> type(x)
<class 'function'>
A function can be called with the parentheses operators, obviously. However, since a function is also an object, you can put that function inside of a variable:
>>> y = x
>>> y()
Hello World
What you're doing with the dict is making key-value pairs: "+" corresponds to the object add; and since add is a function, it can be called.
answered Nov 23 '18 at 0:00
Green Cloak GuyGreen Cloak Guy
2,6181720
answered Nov 23 '18 at 0:00
Green Cloak GuyGreen Cloak Guy
2,6181720
answered Nov 23 '18 at 0:00
Green Cloak GuyGreen Cloak Guy
2,6181720
answered Nov 23 '18 at 0:00
Green Cloak GuyGreen Cloak Guy
2,6181720
2,6181720
add a comment |
add a comment |
To Explain:
The first four functions are making operator functions
Then in the
evaluatefunction, it creates a dictionary, with the signs as key, and the functions as valuesThen, get the
operatorargument, which is one of the signs, so get the value of the key:value pair when the key is that sign, then you just call that value since it's a function
Note that there's a better code, actually operator module contains the first four functions already.
The code for that:
from operator import add,sub,mul,truediv
def evaluate(op1,operator,op2):
ops = {'+':add,'-':sub,'*':mul,'/':truediv}
return ops[operator](op1,op2)
print(evaluate(1,'/',2))
Output:
0.5
answered Nov 22 '18 at 23:55
U9-ForwardU9-Forward
14.8k41338
add a comment |
To Explain:
The first four functions are making operator functions
Then in the
evaluatefunction, it creates a dictionary, with the signs as key, and the functions as valuesThen, get the
operatorargument, which is one of the signs, so get the value of the key:value pair when the key is that sign, then you just call that value since it's a function
Note that there's a better code, actually operator module contains the first four functions already.
The code for that:
from operator import add,sub,mul,truediv
def evaluate(op1,operator,op2):
ops = {'+':add,'-':sub,'*':mul,'/':truediv}
return ops[operator](op1,op2)
print(evaluate(1,'/',2))
Output:
0.5
answered Nov 22 '18 at 23:55
U9-ForwardU9-Forward
14.8k41338
add a comment |
To Explain:
The first four functions are making operator functions
Then in the
evaluatefunction, it creates a dictionary, with the signs as key, and the functions as valuesThen, get the
operatorargument, which is one of the signs, so get the value of the key:value pair when the key is that sign, then you just call that value since it's a function
Note that there's a better code, actually operator module contains the first four functions already.
The code for that:
from operator import add,sub,mul,truediv
def evaluate(op1,operator,op2):
ops = {'+':add,'-':sub,'*':mul,'/':truediv}
return ops[operator](op1,op2)
print(evaluate(1,'/',2))
Output:
0.5
answered Nov 22 '18 at 23:55
U9-ForwardU9-Forward
14.8k41338
To Explain:
The first four functions are making operator functions
Then in the
evaluatefunction, it creates a dictionary, with the signs as key, and the functions as valuesThen, get the
operatorargument, which is one of the signs, so get the value of the key:value pair when the key is that sign, then you just call that value since it's a function
Note that there's a better code, actually operator module contains the first four functions already.
The code for that:
from operator import add,sub,mul,truediv
def evaluate(op1,operator,op2):
ops = {'+':add,'-':sub,'*':mul,'/':truediv}
return ops[operator](op1,op2)
print(evaluate(1,'/',2))
Output:
0.5
answered Nov 22 '18 at 23:55
U9-ForwardU9-Forward
14.8k41338
edited Nov 23 '18 at 0:01
answered Nov 22 '18 at 23:55
U9-ForwardU9-Forward
14.8k41338
answered Nov 22 '18 at 23:55
U9-ForwardU9-Forward
14.8k41338
answered Nov 22 '18 at 23:55
U9-ForwardU9-Forward
14.8k41338
14.8k41338
add a comment |
add a comment |
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1
Functions are objects. They can be assigned, stored, and passed as parameters, just like any other object.
– John Gordon
Nov 22 '18 at 23:57