java and python equivalent of php's foreach($array as $key => $value)

Question

In php, one can handle a list of state names and their abbreviations with an associative array like this:

<?php
    $stateArray = array(
        "ALABAMA"=>"AL",
        "ALASKA"=>"AK",
        // etc...
        "WYOMING"=>"WY"
    );

    foreach ($stateArray as $stateName => $stateAbbreviation){
        print "The abbreviation for $stateName is $stateAbbreviation.\n\n";
    }
?>

Output (with key order preserved):

The abbreviation for ALABAMA is AL.

The abbreviation for ALASKA is AK.

The abbreviation for WYOMING is WY.

EDIT: Note that the order of array elements is preserved in the output of the php version. The Java implementation, using a HashMap, does not guarantee the order of elements. Nor does the dictionary in Python.

How is this done in java and python? I only find approaches that supply the value, given the key, like python's:

stateDict = {
    "ALASKA": "AK",
    "WYOMING": "WY",
}

for key in stateDict:
    value = stateDict[key]

---

EDIT: based on the answers, this was my solution in python,

# a list of two-tuples
stateList = [
    ('ALABAMA', 'AL'),
    ('ALASKA', 'AK'),
    ('WISCONSIN', 'WI'),
    ('WYOMING', 'WY'),
]

for name, abbreviation in stateList:
    print name, abbreviation

Output:

ALABAMA AL
ALASKA AK
WISCONSIN WI
WYOMING WY

Which is exactly what was required.

Answer 1

in Python:

for key, value in stateDict.items(): # .iteritems() in Python 2.x
    print "The abbreviation for %s is %s." % (key, value)

in Java:

Map<String,String> stateDict;

for (Map.Entry<String,String> e : stateDict.entrySet())
    System.out.println("The abbreviation for " + e.getKey() + " is " + e.getValue() + ".");

Answer 2

in java for associative array use Map

import java.util.*;

class Foo
{
    public static void main(String[] args)
    {
        Map<String, String> stateMap = new HashMap<String, String>();
        stateMap.put("ALABAMA", "AL");
        stateMap.put("ALASKA", "AK");
        // ...
        stateMap.put("WYOMING", "WY");

        for (Map.Entry<String, String> state : stateMap.entrySet()) {
             System.out.printf(
                "The abbreviation for %s is %s%n",
                state.getKey(),
                state.getValue()
            );
        }
    }
}

Answer 3

Also, to maintain insertion order, you can use a LinkedHashMap instead of a HashMap.

Answer 4

In python an ordered dictionary is available in Python 2.7 (not yet released) and Python 3.1. It's called OrderedDict.

Answer 5

This is the modified code from o948 where you use a TreeMap instead of a HashMap. The Tree map will preserve the ordering of the keys by the key.

import java.util.*;

class Foo
{
 public static void main(String[] args)
 {
    Map<String, String> stateMap = new TreeMap<String, String>();
    stateMap.put("ALABAMA", "AL");
    stateMap.put("ALASKA", "AK");
    // ...
    stateMap.put("WYOMING", "WY");

    for (Map.Entry<String, String> state : stateMap.entrySet()) {
             System.out.printf(
                    "The abbreviation for %s is %s%n",
                    state.getKey(),
                    state.getValue()
            );
      }
    }
 }

Answer 6

Another way of doing it in Java. Although a better way has already been posted, this one's syntactically closer to your php code.

for (String x:stateDict.keySet()){
        System.out.printf("The abbreviation for %s is %s\n",x,stateDict.get(x));
    }

Answer 7

Along the lines of Alexander's answer...

The native python dictionary doesn't maintain ordering for maximum efficiency of its primary use: an unordered mapping of keys to values.

I can think of two workarounds:

1. look at the source code of OrderedDict and include it in your own program.

2. make a list that holds the keys in order:

   states = ['Alabamba', 'Alaska', ...]  
   statesd = {'Alabamba':'AL', 'Alaska':'AK', ...}
   for k in states:
       print "The abbreviation for %s is %s." % (k, statesd[k])
   

Answer 8

TreeMap is not an answer to your question because it sorts elements by key, while LinkedHashMap preserves original order. However, TreeMap is more suitable for the dictionary because of sorting.