19) The continue statement - The continue statement is used to tell Python to skip the rest of the statements in the current loop block and to continue to the next iteration of the loop.
20) Defining a Function - Functions are reusable pieces of programs. They allow you to give a name to a block of statements and you can run that block using that name anywhere in your program and any number of times. This is known as calling the function. We have already used many built-in functions such as the ‘len and range’. Functions are defined using the def keyword. This is followed by an identifier name for the function followed by a pair of parentheses which may enclose some names of variables and the line ends with a colon.
21) Function Parameters - A function can take parameters which are just values you supply to the function so that the function can do something utilising those values. These parameters are just like variables except that the values of these variables are defined when we call the function and are not assigned values within the function itself.Parameters are specified within the pair of parentheses in the function definition, separated by commas. When we call the function, we supply the values in the same way. Note the terminology used - the names given in the function definition are called parameters whereas the values you supply in the function call are called arguments.
22) Local Variables - When you declare variables inside a function definition, they are not related in any way to other variables with the same names used outside the function i.e. variable names are local to the function. This is called the scope of the variable. All variables have the scope of the block they are declared in starting from the point of definition of the name.
23) Using the global statement - If you want to assign a value to a name defined outside the function, and then you have to tell Python that the name is not local, but it is global. We do this using the global statement. It is impossible to assign a value to a variable defined outside a function without the global statement.
You can use the values of such variables defined outside the function (assuming there is no variable with the same name within the function). However, this is not encouraged and should be avoided since it becomes unclear to the reader of the program as to where that variable's definition is. Using the global statement makes it amply clear that the variable is defined in an outer block.
24) Default Argument Values - For some functions, you may want to make some of its parameters as optional and use default values if the user does not want to provide values for such parameters. This is done with the help of default argument values. You can specify default argument values for parameters by following the parameter name in the function definition with the assignment operator (=) followed by the default value.
Note that the default argument value should be a constant. More precisely, the default argument value should be immutable - this is explained in detail in later chapters. For now, just remember this.
25) Keyword Arguments - If you have some functions with many parameters and you want to specify only some of them, then you can give values for such parameters by naming them - this is called keyword arguments - we use the name (keyword) instead of the position (which we have been using all along) to specify the arguments to the function.
26) There are two advantages - one, using the function is easier since we do not need to worry about the order of the arguments. Two, we can give values to only those parameters which we want, provided that the other parameters have default argument values.
27) The return statement - The return statement is used to return from a function i.e. break out of the function. We can optionally return a value from the function as well.
28) DocStrings - Python has a nifty feature called documentation strings which is usually referred to by its shorter name docstrings. DocStrings are an important tool that you should make use of since it helps to document the program better and makes it more easy to understand.
GitHub: https://github.com/bornfreesoul/Python/blob/master/FiveBox
20) Defining a Function - Functions are reusable pieces of programs. They allow you to give a name to a block of statements and you can run that block using that name anywhere in your program and any number of times. This is known as calling the function. We have already used many built-in functions such as the ‘len and range’. Functions are defined using the def keyword. This is followed by an identifier name for the function followed by a pair of parentheses which may enclose some names of variables and the line ends with a colon.
21) Function Parameters - A function can take parameters which are just values you supply to the function so that the function can do something utilising those values. These parameters are just like variables except that the values of these variables are defined when we call the function and are not assigned values within the function itself.Parameters are specified within the pair of parentheses in the function definition, separated by commas. When we call the function, we supply the values in the same way. Note the terminology used - the names given in the function definition are called parameters whereas the values you supply in the function call are called arguments.
22) Local Variables - When you declare variables inside a function definition, they are not related in any way to other variables with the same names used outside the function i.e. variable names are local to the function. This is called the scope of the variable. All variables have the scope of the block they are declared in starting from the point of definition of the name.
23) Using the global statement - If you want to assign a value to a name defined outside the function, and then you have to tell Python that the name is not local, but it is global. We do this using the global statement. It is impossible to assign a value to a variable defined outside a function without the global statement.
You can use the values of such variables defined outside the function (assuming there is no variable with the same name within the function). However, this is not encouraged and should be avoided since it becomes unclear to the reader of the program as to where that variable's definition is. Using the global statement makes it amply clear that the variable is defined in an outer block.
24) Default Argument Values - For some functions, you may want to make some of its parameters as optional and use default values if the user does not want to provide values for such parameters. This is done with the help of default argument values. You can specify default argument values for parameters by following the parameter name in the function definition with the assignment operator (=) followed by the default value.
Note that the default argument value should be a constant. More precisely, the default argument value should be immutable - this is explained in detail in later chapters. For now, just remember this.
25) Keyword Arguments - If you have some functions with many parameters and you want to specify only some of them, then you can give values for such parameters by naming them - this is called keyword arguments - we use the name (keyword) instead of the position (which we have been using all along) to specify the arguments to the function.
26) There are two advantages - one, using the function is easier since we do not need to worry about the order of the arguments. Two, we can give values to only those parameters which we want, provided that the other parameters have default argument values.
27) The return statement - The return statement is used to return from a function i.e. break out of the function. We can optionally return a value from the function as well.
28) DocStrings - Python has a nifty feature called documentation strings which is usually referred to by its shorter name docstrings. DocStrings are an important tool that you should make use of since it helps to document the program better and makes it more easy to understand.
GitHub: https://github.com/bornfreesoul/Python/blob/master/FiveBox
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