Scope¶
you can watch parallel the video for C/C++ (german): https://www.youtube.com/watch?v=JDDWSWef0ng&list=PLEWVM-KBUSpmWSfyoFdD_hLWAY_9tTgi5&index=12
The scopes are implemented with a stack implemented with the CPU. https://de.wikipedia.org/wiki/Stapelspeicher#/media/Datei:ProgramCallStack2_en.svg
In [1]:
import ROOT
In [2]:
import fortranmagic
%load_ext fortranmagic
import os
import sys
import numpy as np
if sys.platform.startswith("win"):
# Depends of system, python builds, and compilers compatibility.
# See below.
f_config = "--fcompiler=gnu95 --compiler=mingw32"
else:
# For Unix, compilers are usually more compatible.
f_config = ""
# Disable only deprecated NumPy API warning without disable any APIs.
f_config += " --extra '-DNPY_NO_DEPRECATED_API=0'"
%fortran_config {f_config}
%load_ext rpy2.ipython
New default arguments for %fortran: --extra '-DNPY_NO_DEPRECATED_API=0'
Error importing in API mode: ImportError('/home/k/miniforge3/envs/ROOT/lib/python3.14/site-packages/_rinterface_cffi_api.abi3.so: undefined symbol: R_ClosureEnv')
Trying to import in ABI mode.
C++¶
In [3]:
%%cpp
#include <iostream>
using namespace std;
int g=40;
//int main(int argc,char *argv[])
{
cout <<"in main before local variable definition: "<<g<<endl;
int g=42; //the local scope does not overrides the global scope
cout <<"in main after local variable definition: "<<g<<endl;
{
cout <<"in subscope before local variable: "<<g<<endl;
int g=43;
cout <<"in subscope after local variable: "<<g<<endl;
}
cout<<"in main after subscope: "<<g<<endl;
}
in main before local variable definition: 40 in main after local variable definition: 42 in subscope before local variable: 42 in subscope after local variable: 43 in main after subscope: 42
C¶
In [4]:
%%cpp
#include <stdio.h>
int g=40;
//int main(int argc,char *argv[])
{
//printf("in main before local variable definition: %d\n",g); //this is not allowed in c, the definitions must come first
int g=42; //the local scope does not overrides the global scope
printf("in main after local variable definition: %d\n",g); //this is not allowed in c
{
//printf("in subscope before local variable: %d\n",g); //this is not allowed in c
int g=43;
printf("in subscope after local variable: %d\n",g);
}
printf("in main after subscope: %d\n",g);
}
in main after local variable definition: 42 in subscope after local variable: 43 in main after subscope: 42
Javascript¶
javascript also has local scope as in c if defined with let
In [5]:
%%js //the next line is only necessary in jupyter notebooks
element.setAttribute('style', 'white-space: pre;');console.log=function(text){element.textContent+=text+"\n"}
let g=40
{
console.log(g)
g=41
console.log(g)
}
console.log(g)
In [6]:
%%js //the next line is only necessary in jupyter notebooks
element.setAttribute('style', 'white-space: pre;');console.log=function(text){element.textContent+=text+"\n"}
let g=40
{
//console.log(g) //not allowed
let g=41
{
let g=42;
console.log(g);
}
console.log(g)
}
console.log(g)
In [7]:
%%js //the next line is only necessary in jupyter notebooks
element.setAttribute('style', 'white-space: pre;');console.log=function(text){element.textContent+=text+"\n"}
{
//console.log(g) //not allowed
var g=41 //defines a global variable but not when used inside a function!
{
let g=42;
console.log(g);
}
console.log(g)
}
console.log(g)
In [8]:
%%js //the next line is only necessary in jupyter notebooks
element.setAttribute('style', 'white-space: pre;');console.log=function(text){element.textContent+=text+"\n"}
//Variables declared with var, let and const are quite similar when declared inside a function.
let g=40;
function test(){
var g=42;
{
//console.log(g); //not allowed
let g=43;
console.log(g);
}
console.log(g)
}
test()
console.log(g)
Python¶
Python only knows three scopes: global, local and class. In python scopes are defined by indentation. It is important to keep a consistent indentation. We need to use functions to show the scopes.
In [9]:
g=40
def myfunc():
g = 42
def myinnerfunc():
print(g)
myinnerfunc()
print(g)
myfunc()
print(g)
42 42 40
In [10]:
g=40
def myfunc():
g = 42
def myinnerfunc():
g=43
print(g)
myinnerfunc()
print(g)
myfunc()
print(g)
43 42 40
In [11]:
def myfunc():
g = 42
def myinnerfunc():
print(g) #not allowed
g=43
print(g)
myinnerfunc()
print(g)
myfunc()
--------------------------------------------------------------------------- UnboundLocalError Traceback (most recent call last) Cell In[11], line 10 6 print(g) 7 myinnerfunc() 8 print(g) 9 ---> 10 myfunc() Cell In[11], line 7, in myfunc() 3 def myinnerfunc(): 4 print(g) #not allowed 5 g=43 6 print(g) ----> 7 myinnerfunc() 8 print(g) Cell In[11], line 4, in myfunc.<locals>.myinnerfunc() 3 def myinnerfunc(): ----> 4 print(g) #not allowed 5 g=43 6 print(g) UnboundLocalError: cannot access local variable 'g' where it is not associated with a value
In [12]:
g=40
def myfunc():
g = 42
def myinnerfunc():
global g #this is accessing the global g
g=43
print(g)
myinnerfunc()
print(g)
myfunc()
print(g)
43 42 43
R¶
In [13]:
%%R
g <- 40
myfunc <- function() {
g <- 42
myinnerfunc <- function() {
print(g)
}
myinnerfunc()
print(g)
}
myfunc()
print(g)
[1] 42 [1] 42 [1] 40
In [14]:
%%R
g <- 40
myfunc <- function() {
g <- 42
myinnerfunc <- function() {
g<-43
print(g)
}
myinnerfunc()
print(g)
}
myfunc()
print(g)
[1] 43 [1] 42 [1] 40
In [ ]:
In [15]:
%%R
g <- 40
myfunc <- function() {
g <- 42
myinnerfunc <- function() {
print(g)
g<-43
print(g)
}
myinnerfunc()
print(g)
}
myfunc()
print(g)
[1] 42 [1] 43 [1] 42 [1] 40
In [19]:
%%R
g <- 40
myfunc <- function() {
g <- 42 #myfunc scope variable g
myinnerfunc <- function() {
g<-42
g<<-44 # this is accessing myfunc scope variable g
assign("g", 43, envir = .GlobalEnv) # like Python: global g
print(get("g", envir = .GlobalEnv))
print(g)
}
myinnerfunc()
print(g)
}
myfunc()
print(g)
[1] 43 [1] 42 [1] 44 [1] 43
Fortran¶
Fortan does only have function scopes