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Python Variables and Expressions
# Declare a variable and initialize it
v = 1
print(v)Output:
1 (Integer)# Declare a variable and initialize it
v = 1
print(v)
# re-declaring the variable works
v = "abc"
print(v)Output:
abc (String)So even if the variable has already been declared you can simply redeclare it and that works.
# ERROR: variables of different types cannot be combined
print( "abc" + 1 )Output:
error TypeError: can only concatenate str (not "int") to strThis is happening because Python is a strongly typed language even though you don't have to declare the type of a variable before you use it. What's happening is when Python goes to execute the code it infers a specific type for a value or a variable. You can't go back and change the type or combine it with other types.
# Global vs. local variables in functions
Variable = "ABC"
#Define Some Function
def Function():
Variable = "XYZ"
print(Variable)
#End of Function
Function()
print(Variable)Output:
XYZ
ABCThe reason is because inside the function the function gets it own local copy of whatever variables you declare inside the function. So the two variables even if they have the same name are considered two separate variables by the Python interpreter.
# Global vs. local variables in functions
Variable = "ABC"
#Define Some Function
def Function():
global Variable
Variable = "XYZ"
print(Variable)
#End of Function
Function()
print(Variable)Output:
XYZ
XYZThe function here is now operating on the global variable. Since we told the function that Variable is now global this assignment
Variable = "Local" affects the Variable that's outside the function.# Global vs. local variables in functions
Variable = "ABC"
#Define Some Function
def Function():
global Variable
Variable = "XYZ"
print(Variable)
#End of Function
Function()
print(Variable)
#Delete Variable Definition
del Variable
print(Variable)Output:
XYZ
XYZ
NameError: name 'Variable' is not definedSo essentially what this means is that you can undefine variables in real time by using the del statement.
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