{"id":1689,"date":"2011-04-16T15:21:55","date_gmt":"2011-04-16T15:21:55","guid":{"rendered":"http:\/\/cemclinux1.math.uwaterloo.ca\/~cscircles\/wordpress\/?page_id=1689"},"modified":"2011-04-16T15:21:55","modified_gmt":"2011-04-16T15:21:55","slug":"13-lists","status":"publish","type":"page","link":"https:\/\/olescs.hkmu.edu.hk\/python\/13-lists\/","title":{"rendered":"13: Lists (Arrays)"},"content":{"rendered":"\n

A list<\/strong> is a sequence of several variables, grouped together under a single name. Instead of writing a program with many variables x0<\/code>, x1<\/code>, x2<\/code>, \u2026 you can define a single variable x<\/code> and access its members x[0]<\/code>, x[1]<\/code>, x[2]<\/code>, etc. More importantly, you can put other expressions and variables inside the square brackets, like x[i]<\/code> and x[i+1]<\/code>. This allows us to deal with arbitrarily large data sets using just a single small piece of code.<\/p>\n

One way to create a list is by enclosing several values, separated with commas, between square brackets:<\/p>\n

myList = [\"the first value in the list\", 1999, 4.5]<\/pre>This creates a list called\u00a0myList<\/code> of length 3. Each element of the list gets a number called its\u00a0index<\/strong>: the initial element has index 0, the next element has index 1, and so forth. The individual variables comprising the list have the names<\/p>\n
\u00ablistName\u00bb[\u00abindexNumber\u00bb]<\/code><\/p>\n
So in this example, myList[0]<\/code> is a variable whose value is the string\u00a0\"the first value in the list\"<\/code> and print(myList[2])<\/code> would print<\/a> 4.5<\/code>. You can also change the values of items in the list, and print out entire lists:<\/p>\n
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Example<\/span><\/div>Updating and printing a list.