Re: [Tutor] foreach loops

[Alan Gauld]

 Does python have foreach loops?  I don't see any
 mention of them in the docs.  Am I going to have to
 use Perl (gasp!) if I want my beloved foreach loop?

Its called a for loop in Python...

Or is there some extra magic in the Perl version that I'm missing?

Alan G.
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Re: [Tutor] foreach loops

[Alan Gauld]

 I was thinking more along the lines of this:
 
 A C++ for loop:

This is exactly NOT a foreach loop, its a vanilla for loop.

 
 #include iostream
 
 using std::cout;
 
 int main() {
 
 for (int i = 0; i  10; i++) {
 cout  i  \n;
 }

for i in range(10): print i

Alan G.
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Re: [Tutor] foreach loops

[Danny Yoo]

 Does python have foreach loops?  I don't see any mention of them in the 
 docs.  Am I going to have to use Perl (gasp!) if I want my beloved 
 foreach loop?

Can you show an example of a Perl foreach loop?  Perhaps someone can help 
translate it into idiomatic Python.

Good luck!
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Re: [Tutor] foreach loops

[Luke Paireepinart]

Danny Yoo wrote:
   
 Does python have foreach loops?  I don't see any mention of them in the 
 docs.  Am I going to have to use Perl (gasp!) if I want my beloved 
 foreach loop?
 

 Can you show an example of a Perl foreach loop?  Perhaps someone can help 
 translate it into idiomatic Python.
   
It seems to me that foreach is the same as the python 'for' loop
#-- perl code
@myNames = ('Larry', 'Curly', 'Moe');
print Who's on the list:\n; foreach (@myNames) {
print $_ . \n;
}

#--- python code:
names = ['Larry','Curly','Moe']
print Who's on the list?\n
for x in mynames:
print x+'\n'
#

Am I missing the point here?
-Luke
 Good luck!
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Re: [Tutor] foreach loops

[Luke Paireepinart]

Christopher Spears wrote:
 Hmmm...Perl is probably a bad example.  My apologies. 
 I was thinking more along the lines of this:

 A C++ for loop:

 #include iostream

 using std::cout;

 int main() {
   
   for (int i = 0; i  10; i++) {
   cout  i  \n;
   }
   
   return 0; 
 }

   
for i in range(10):
print i+'\n'


that does the same thing as
a = [0,1,2,3,4,5,6,7,8,9]
for i in a:
print i+'\n'

or
a = range(10)
for i in a:
print i+'\n'

Python's 'for' loop is not really meant as an iterator over a list of 
numbers
so this feature isn't built into the loop itself, you have to use the 
range function,
which just generates a list of numbers to iterate over.


Perhaps you should read an introductory Python tutorial.
Any one of them should cover the types of questions that people from 
other languages have about Python.
It sounds like you know how to program already, so the 'python for 
non-programmers' type of tutorial
may not be best-suited to you, but just look around.
If you have any more questions I'd be happy to answer them,
as would the rest of the list, I'm sure.

HTH,
-Luke

   

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Re: [Tutor] foreach loops

[Jordan Greenberg]

Christopher Spears wrote:
 Hmmm...Perl is probably a bad example.  My apologies. 
 I was thinking more along the lines of this:
 
 A C++ for loop:
 
 #include iostream
 
 using std::cout;
 
 int main() {
   
   for (int i = 0; i  10; i++) {
   cout  i  \n;
   }
   
   return 0; 
 }
 
The same functionality can be provided using python for and the range()
function, like:

for i in range(0, 10):
print i


Though because of the way python works you don't need to use this type
of loop anywhere near as often as in other languages. For example in
java (and c++, but my c++ is so rusty I'm not going embarrass myself
trying to write an example) you're constantly doing things like looping
over an array:

public void main(String[] args) {
int[] foo;

/* then later after foo has been initialized to whatever: */

for (int i=0; ifoo.length; i++) {
System.out.println(foo[i]);
}
}

The equivalent code in python is much cleaner, after foo has been
initialized to whatever:

for each in foo:
print each


Hope this helps,
Jordan Greenberg





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