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

问题

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.

回答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() + ".");

回答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()
            );
        }
    }
}

回答3:

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

回答4:

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

回答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()
            );
      }
    }
 }

回答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));
    }

回答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])
   

回答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.

来源：https://stackoverflow.com/questions/1219548/java-and-python-equivalent-of-phps-foreacharray-as-key-value