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Tkinter (view source)

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Use [[VSCodium]] or any [[ource-code editor]] to edit your [[source code]]s.
Use [[VSCodium]] or any [[source-code editor]] to edit your [[source code]]s.




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== GUI calculator ==
== GUI calculator ==
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=== Source code ===
=== Source code ===
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  app = MyApp()
  app = MyApp()
  app.mainloop()
  app.mainloop()
==== return ====
Why would you use the return statement in Python?
The print() function writes, i.e., "prints", a string or a number on the console. The return statement does not print out the value it returns when the function is called. It however causes the function to exit or terminate immediately, even if it is not the last statement of the function.
Functions that return values are sometimes called fruitful functions. In many other languages, a function that doesn’t return a value is called a procedure.
In the given code the value returned (that is 2) when function foo() is called is used in the function bar(). These return values are printed on console only when the print statements are used as shown below.
Example
def foo():
    print("Hello from within foo")
    return 2
def bar():
    return 10*foo()
print(foo())
print(bar())
Output
Hello from within foo
2
Hello from within foo
20
We see that when foo() is called from bar(), 2 isn't written to the console. Instead it is used to calculate the value returned from bar().
https://www.tutorialspoint.com/Why-would-you-use-the-return-statement-in-Python




==== functools.partial ====
==== functools.partial ====
Partial functions
You can create partial functions in python by using the partial function from the functools library.
Partial functions allow one to derive a function with x parameters to a function with fewer parameters and fixed values set for the more limited function.
Import required:
from functools import partial
This code will return 21.
from functools import partial
def multiply(x,y):
    return x * y
loli = partial(multiply,3)
print(loli(7))
7*3 = 21
An important note: the default values will start replacing variables from the left. The 2 will replace x. y will equal 4 when dbl(4) is called. It does not make a difference in this example, but it does in the example below.
Exercise
Edit the function provided by calling partial() and replacing the first three variables in func(). Then print with the new partial function using only one input variable so that the output equals 26.
#Following is the exercise, function provided:
from functools import partial
def func(u,v,w,x):
    return u*5 + v*4 + w*3 + x
#Enter your code here to create and print with your partial function
baby = partial(func,1,2,3)
print(baby(4))
1*5 + 2*4 + 3*3 + 4 = 26
functools — Higher-order functions and operations on callable objects
functools — Higher-order functions and operations on callable objects


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  if not type(x) is int:
  if not type(x) is int:
   raise TypeError("Only integers are allowed")
   raise TypeError("Only integers are allowed")
=== Python eval() ===
The eval() method parses the expression passed to this method and runs python expression (code) within the program.
In simple terms, the eval() method runs the python code (which is passed as an argument) within the program.
The syntax of eval() is:
eval(expression, globals=None, locals=None)
eval() Parameters
The eval() takes three parameters:
* expression - this string as parsed and evaluated as a Python expression
* globals (optional) - a dictionary
* locals (optional)- a mapping object. Dictionary is the standard and commonly used mapping type in Python.
The use of "globals" and "locals" will be discussed later in this article.
Return Value from eval()
The eval() method returns the result evaluated from the "expression".
Example 1: How eval() works in Python?
x = 2
print(eval('x + 1'))
When you run the program, the output will be:
3
Here, the eval() evaluates the expression "x + 1" and print it.
Example 2: Practical Example to Demonstrate Use of eval()
# Calculate perimeter of square
def calPeri(L):
    return 4*L
# Calculate area of square
def calArea(L):
    return L*L
property = input("Type a function: ")
for L in range(1, 5):
    if (property == 'calPeri(L)'):
        print("If length is ", L, ", perimeter is ", eval(property), ".")
    elif (property == 'calArea(L)'):
        print("If length is ", L, ", area is ", eval(property), ".")
    else:
        print('Wrong Function')
        break
The output of the above program will be:
Type a function: calPeri(L)
If length is  1 , perimeter is  4 .
If length is  2 , perimeter is  8 .
If length is  3 , perimeter is  12 .
If length is  4 , perimeter is  16 .
or
Type a function: calArea(L)
If length is  1 , area is  1 .
If length is  2 , area is  4 .
If length is  3 , area is  9 .
If length is  4 , area is  16 .
Why you should be careful while using eval()?
Consider a situation, you are using a [[Unix]] system ([[macOS]], [[Linux]] etc) and you have imported "os" module. The os module provides portable way to use operating system functionalities like: read or write a file.
If you allow users to input a value using "eval(input())", the user may issue commands to change file or even delete all the files using command "os.system('rm -rf *')".
https://www.programiz.com/python-programming/methods/built-in/eval


== See also ==
== See also ==
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:* [[Linux]]
:* [[Linux]]
* [[Windows]] ([[Microsoft Windows]])
* [[Windows]] ([[Microsoft Windows]])
* [[Artificial intelligence]]
:* [[Statistics]]
:* [[Machine learning]]


== References ==
== References ==
Gyesnyrre
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