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Python Programming Essentials - M19 - Namespaces, Global Variables and Docstrings
This document discusses namespaces, global variables, and docstrings in Python. It explains that namespaces are like dictionaries that keep track of variable names and values. There are local, global, and built-in namespaces. Variables defined outside functions are global and can be accessed from anywhere, but reassigned locally without changing the global value unless declared global. Docstrings provide documentation for modules, functions, classes and are accessed with object.__doc__.
In this document
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Introduction to Skillbrew, Python programming essentials, and presenter Pavan Verma.
Namespaces in Python manage variable scopes, categorized as Local, Global, and Built-in.
Explains the order of variable lookup: Local, Global, and Built-in with an example function using local variables.
Definition of global variables, illustrating their behavior inside and outside functions with examples.
Docstrings in Python allow documentation association with code, enhancing code readability.
Lists resources for further reading on local variables and docstrings in Python.
Python Programming Essentials - M19 - Namespaces, Global Variables and Docstrings
- 1. http://www.skillbrew.com /Skillbrew Talent brewed bythe industry itself Namespaces, global variables and Docstrings Pavan Verma @YinYangPavan Founder, P3 InfoTech Solutions Pvt. Ltd. 1 Python Programming Essentials
- 2. © SkillBrew http://skillbrew.com Namespaces 1.Python uses what are called namespaces to keep track of variables. 2. A namespace is just like a dictionary where the keys are names of variables and the dictionary values are the values of those variables. 2
- 3. © SkillBrew http://skillbrew.com Namespaces Local Namespace Global Namespace Built-in Namespace specificto the current function or class method specific to the current module global to all modules 3
- 4. © SkillBrew http://skillbrew.com Orderof a lookup Local Namespace Global Namespace Built-in Namespace def printList(upper_limit, step=2): # variables upper_limit and step belong to this function’s local namespace. print "upper limit: %d" % upper_limit num_list = range(0, upper_limit, step) print num_list printList(upper_limit=5, step=2) a = "foo" b = "bar" # variables a, b and function printList belong to Global namespace of this module 4
- 5. © SkillBrew http://skillbrew.com Globalvariables counter = 10 def printVar(): print counter printVar() print "counter: %d" % counter Output: 10 counter: 10 Variable defined outside a function or class is a global variable. Counter is a global variable 5
- 6. © SkillBrew http://skillbrew.com Globalvariables counter = 10 def printVar(): counter = 20 print "Counter in: %d" % counter printVar() print "counter out: %d" % counter Output: Counter in: 20 counter out: 10 counter in function definition is local variable tied to function’s namespace. Hence the value of global counter does not gets modified. 6
- 7. © SkillBrew http://skillbrew.com Globalvariables counter = 10 def printVar(): global counter counter = 20 print "Counter in: %d" % counter printVar() print "counter out: %d" % counter Output: counter in: 20 counter out: 20 In order to use the global counter variable inside the function you have to explicitly tell python to use global variable using global keyword. 7
- 8. © SkillBrew http://skillbrew.com Docstrings defadd(x, y): """ Return the sum of inputs x, y """ return x + y print add.__doc__ Python documentation strings (or docstrings) provide a convenient way of associating documentation with Python modules, functions, classes, and methods. docstri Access a docstring using object.__doc__ 8
- 9. © SkillBrew http://skillbrew.com Resources http://www.ibiblio.org/g2swap/byteofpyt hon/read/local-variables.html http://www.ibiblio.org/g2swap/byteofpyt hon/read/docstrings.html 9