Is there a zip-like method in .Net?
Question:
In Python there is a really neat function called zip
which can be used to iterate through two lists at the same time:
list1 = [1, 2, 3]
list2 = ["a", "b", "c"]
for v1, v2 in zip(list1, list2):
print v1 + " " + v2
The above code should produce the following:
1 a
2 b
3 c
I wonder if there is a method like it available in .Net? I’m thinking about writing it myself, but there is no point if it’s already available.
Answers:
Nope, there is no such function in .NET. You have roll out your own. Note that C# doesn’t support tuples, so python-like syntax sugar is missing too.
You can use something like this:
class Pair<T1, T2>
{
public T1 First { get; set;}
public T2 Second { get; set;}
}
static IEnumerable<Pair<T1, T2>> Zip<T1, T2>(IEnumerable<T1> first, IEnumerable<T2> second)
{
if (first.Count() != second.Count())
throw new ArgumentException("Blah blah");
using (IEnumerator<T1> e1 = first.GetEnumerator())
using (IEnumerator<T2> e2 = second.GetEnumerator())
{
while (e1.MoveNext() && e2.MoveNext())
{
yield return new Pair<T1, T2>() {First = e1.Current, Second = e2.Current};
}
}
}
...
var ints = new int[] {1, 2, 3};
var strings = new string[] {"A", "B", "C"};
foreach (var pair in Zip(ints, strings))
{
Console.WriteLine(pair.First + ":" + pair.Second);
}
Update: It is built-in in C# 4 as System.Linq.Enumerable.Zip<TFirst, TSecond, TResult> Method
Here is a C# 3 version:
IEnumerable<TResult> Zip<TResult,T1,T2>
(IEnumerable<T1> a,
IEnumerable<T2> b,
Func<T1,T2,TResult> combine)
{
using (var f = a.GetEnumerator())
using (var s = b.GetEnumerator())
{
while (f.MoveNext() && s.MoveNext())
yield return combine(f.Current, s.Current);
}
}
Dropped the C# 2 version as it was showing its age.
As far as I know there is not. I wrote one for myself (as well as a few other useful extensions and put them in a project called NExtension on Codeplex.
Apparently the Parallel extensions for .NET have a Zip function.
Here’s a simplified version from NExtension (but please check it out for more useful extension methods):
public static IEnumerable<TResult> Zip<T1, T2, TResult>(this IEnumerable<T1> source1, IEnumerable<T2> source2, Func<T1, T2, TResult> combine)
{
using (IEnumerator<T1> data1 = source1.GetEnumerator())
using (IEnumerator<T2> data2 = source2.GetEnumerator())
while (data1.MoveNext() && data2.MoveNext())
{
yield return combine(data1.Current, data2.Current);
}
}
Usage:
int[] list1 = new int[] {1, 2, 3};
string[] list2 = new string[] {"a", "b", "c"};
foreach (var result in list1.Zip(list2, (i, s) => i.ToString() + " " + s))
Console.WriteLine(result);
There’s also one in F#:
let zipped = Seq.zip firstEnumeration secondEnumation
let zipped = Seq.zip firstEnumeration secondEnumation
In Python there is a really neat function called zip
which can be used to iterate through two lists at the same time:
list1 = [1, 2, 3]
list2 = ["a", "b", "c"]
for v1, v2 in zip(list1, list2):
print v1 + " " + v2
The above code should produce the following:
1 a 2 b 3 c
I wonder if there is a method like it available in .Net? I’m thinking about writing it myself, but there is no point if it’s already available.
Nope, there is no such function in .NET. You have roll out your own. Note that C# doesn’t support tuples, so python-like syntax sugar is missing too.
You can use something like this:
class Pair<T1, T2>
{
public T1 First { get; set;}
public T2 Second { get; set;}
}
static IEnumerable<Pair<T1, T2>> Zip<T1, T2>(IEnumerable<T1> first, IEnumerable<T2> second)
{
if (first.Count() != second.Count())
throw new ArgumentException("Blah blah");
using (IEnumerator<T1> e1 = first.GetEnumerator())
using (IEnumerator<T2> e2 = second.GetEnumerator())
{
while (e1.MoveNext() && e2.MoveNext())
{
yield return new Pair<T1, T2>() {First = e1.Current, Second = e2.Current};
}
}
}
...
var ints = new int[] {1, 2, 3};
var strings = new string[] {"A", "B", "C"};
foreach (var pair in Zip(ints, strings))
{
Console.WriteLine(pair.First + ":" + pair.Second);
}
Update: It is built-in in C# 4 as System.Linq.Enumerable.Zip<TFirst, TSecond, TResult> Method
Here is a C# 3 version:
IEnumerable<TResult> Zip<TResult,T1,T2>
(IEnumerable<T1> a,
IEnumerable<T2> b,
Func<T1,T2,TResult> combine)
{
using (var f = a.GetEnumerator())
using (var s = b.GetEnumerator())
{
while (f.MoveNext() && s.MoveNext())
yield return combine(f.Current, s.Current);
}
}
Dropped the C# 2 version as it was showing its age.
As far as I know there is not. I wrote one for myself (as well as a few other useful extensions and put them in a project called NExtension on Codeplex.
Apparently the Parallel extensions for .NET have a Zip function.
Here’s a simplified version from NExtension (but please check it out for more useful extension methods):
public static IEnumerable<TResult> Zip<T1, T2, TResult>(this IEnumerable<T1> source1, IEnumerable<T2> source2, Func<T1, T2, TResult> combine)
{
using (IEnumerator<T1> data1 = source1.GetEnumerator())
using (IEnumerator<T2> data2 = source2.GetEnumerator())
while (data1.MoveNext() && data2.MoveNext())
{
yield return combine(data1.Current, data2.Current);
}
}
Usage:
int[] list1 = new int[] {1, 2, 3};
string[] list2 = new string[] {"a", "b", "c"};
foreach (var result in list1.Zip(list2, (i, s) => i.ToString() + " " + s))
Console.WriteLine(result);
There’s also one in F#:
let zipped = Seq.zip firstEnumeration secondEnumation
let zipped = Seq.zip firstEnumeration secondEnumation