Difference between revisions of "Global & Parameter Passing - Python"
(Created page with "=Global Variables= One way to pass values into subroutines is by using global. In the example below we have declared a variable and we have 2 subroutines which use this, one t...") |
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=Global Variables= | =Global Variables= | ||
| − | One way to pass values into subroutines is by using global. In the example below we have declared a variable and we have 2 subroutines which use this, one to just print and the other to change the value: | + | One way to pass values into subroutines is by using global. Global variables are available throughout the program without the need to include them in the parameters. In the example below we have declared a variable and we have 2 subroutines which use this, one to just print and the other to change the value: |
<syntaxhighlight lang=python> | <syntaxhighlight lang=python> | ||
| Line 32: | Line 32: | ||
This code will print '42' because the variable will be changed in func1(). | This code will print '42' because the variable will be changed in func1(). | ||
| + | |||
| + | =Parameters= | ||
| + | |||
| + | In python a subroutine can have parameters which must be passed into the subroutine when it is called. Failure to do so will cause a syntax error. For example you could create a subroutine and pass it a value as a parameter, this is the subroutine: | ||
| + | |||
| + | <syntaxhighlight lang=python> | ||
| + | def answer(person): | ||
| + | if person=="Wayne": | ||
| + | print("yes") | ||
| + | else: | ||
| + | print("no") | ||
| + | </syntaxhighlight> | ||
| + | |||
| + | You would pass the value when you call the subroutine: | ||
| + | |||
| + | <syntaxhighlight lang=python> | ||
| + | answer(name) | ||
| + | </syntaxhighlight> | ||
| + | |||
| + | Or: | ||
| + | |||
| + | <syntaxhighlight lang=python> | ||
| + | answer("Wayne") | ||
| + | </syntaxhighlight> | ||
| + | |||
| + | =Default Parameters= | ||
| + | You can specify a default value for a parameter, this will be used if no parameter is passed. For example: | ||
| + | |||
| + | <syntaxhighlight lang=python> | ||
| + | def my_function(country = "Norway"): | ||
| + | print("I am from " + country) | ||
| + | |||
| + | my_function("Sweden") | ||
| + | my_function("India") | ||
| + | my_function() | ||
| + | my_function("Brazil") | ||
| + | </syntaxhighlight> | ||
Latest revision as of 13:30, 6 April 2019
Global Variables
One way to pass values into subroutines is by using global. Global variables are available throughout the program without the need to include them in the parameters. In the example below we have declared a variable and we have 2 subroutines which use this, one to just print and the other to change the value:
myGlobal = 5
def func1():
myGlobal = 42
def func2():
print myGlobal
func1()
func2()
This program will actually print '5' and not 42, because the change within func1() is not retained. However it will be if you add a global command:
myGlobal = 5
def func1():
global myGlobal
myGlobal = 42
def func2():
print myGlobal
func1()
func2()
This code will print '42' because the variable will be changed in func1().
Parameters
In python a subroutine can have parameters which must be passed into the subroutine when it is called. Failure to do so will cause a syntax error. For example you could create a subroutine and pass it a value as a parameter, this is the subroutine:
def answer(person):
if person=="Wayne":
print("yes")
else:
print("no")
You would pass the value when you call the subroutine:
answer(name)
Or:
answer("Wayne")
Default Parameters
You can specify a default value for a parameter, this will be used if no parameter is passed. For example:
def my_function(country = "Norway"):
print("I am from " + country)
my_function("Sweden")
my_function("India")
my_function()
my_function("Brazil")
