Generators can only yield ints?

[defn noob]

def letters():
a = xrange(ord('a'), ord('z')+1)
B = xrange(ord('A'), ord('Z')+1)
while True:
yield chr(a)
yield chr(B)

>>l = letters()
l.next()

Traceback (most recent call last):
File "<pyshell#225>", line 1, in <module>
l.next()
File "<pyshell#223>", line 5, in letters
yield chr(a)
TypeError: an integer is required

>>>

Any way to get around this?

[bearophileHUGS]

defn noob:

Any way to get around this?

Your code is wrong, this is one of the correct versions:

from itertools import izip

def letters():
lower = xrange(ord('a'), ord('z')+1)
upper = xrange(ord('A'), ord('Z')+1)
for lc, uc in izip(lower, upper):
yield chr(lc)
yield chr(uc)

print list(letters())

There are other ways to do the same thing.

Bye,
bearophile

[Medardo Rodriguez (Merchise Group)]

On Fri, Aug 22, 2008 at 6:44 PM, defn noob <ci**********@yahoo.sewrote:

def letters():
a = xrange(ord('a'), ord('z')+1)
B = xrange(ord('A'), ord('Z')+1)
while True:
yield chr(a)
yield chr(B)
TypeError: an integer is required

No. The problem is that "chr function" receives "int"
"a" and "B" are generators of "int" items.

What exactly you intent with that code?

Maybe:
#<code>
def letters():
for i in xrange(ord('a'), ord('z')+1):
yield chr(i)
for i in xrange(ord('A'), ord('Z')+1):
yield chr(i)

for letter in letters():
print letter
#</code>

Regards

[Wojtek Walczak]

On Fri, 22 Aug 2008 15:44:15 -0700 (PDT), defn noob wrote:

def letters():
a = xrange(ord('a'), ord('z')+1)
B = xrange(ord('A'), ord('Z')+1)
while True:
yield chr(a)
yield chr(B)

>>>l = letters()
l.next()

Traceback (most recent call last):
File "<pyshell#225>", line 1, in <module>
l.next()
File "<pyshell#223>", line 5, in letters
yield chr(a)
TypeError: an integer is required

>>>>

The error you're seeing is a result of passing
non-integer to chr() function, it has nothing to do
with generators:

>>chr([])

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: an integer is required

>>>

I have simplified your code a bit:
-------------
import string
def letters():
a, B = (string.letters,) * 2
for i in zip(a, B):
yield i[0]
yield i[1]

l = letters()

print l.next()
print l.next()
print l.next()
--------------

and the output:

$ python genlet.py
a
a
b
$

Is that what you tried to achieve?

--
Regards,
Wojtek Walczak,
http://tosh.pl/gminick/

[Steven D'Aprano]

On Fri, 22 Aug 2008 15:44:15 -0700, defn noob wrote:

def letters():
a = xrange(ord('a'), ord('z')+1)
B = xrange(ord('A'), ord('Z')+1)
while True:
yield chr(a)
yield chr(B)

>>>l = letters()
l.next()

Traceback (most recent call last):
File "<pyshell#225>", line 1, in <module>
l.next()
File "<pyshell#223>", line 5, in letters
yield chr(a)
TypeError: an integer is required

>>>>

Any way to get around this?

Yes, write code that isn't buggy :)

Generators can return anything you want. Your problem is that you're
passing an xrange object to chr() instead of an int. Try this:

def letters():
a = xrange(ord('a'), ord('z')+1)
B = xrange(ord('A'), ord('Z')+1)
for t in zip(a, B):
yield chr(t[0])
yield chr(t[1])

But (arguably) a better way is:

def letters():
from string import ascii_letters as letters
for a,b in zip(letters[0:26], letters[26:]):
yield a
yield b
Note that it is important to use ascii_letters rather than letters,
because in some locales the number of uppercase and lowercase letters
differ.
--
Steven

[Lie]

On Aug 23, 5:44*am, defn noob <[e-mail]:

def letters():
* * * * a = xrange(ord('a'), ord('z')+1)
* * * * B = xrange(ord('A'), ord('Z')+1)
* * * * while True:
* * * * * * * * yield chr(a)
* * * * * * * * yield chr(B)

>l = letters()
l.next()

Traceback (most recent call last):
* File "<pyshell#225>", line 1, in <module>
* * l.next()
* File "<pyshell#223>", line 5, in letters
* * yield chr(a)
TypeError: an integer is required

Any way to get around this?

The most direct translation on what you've done, with corrections, is
either this:

def letters():
a = xrange(ord('a'), ord('z') + 1)
B = xrange(ord('A'), ord('Z') + 1)
while True:
yield a
yield B

>>l = letters()
l.next()

xrange(97, 123)

or this:

def letters():
a = xrange(ord('a'), ord('z') + 1)
B = xrange(ord('A'), ord('Z') + 1)
while True:
yield [chr(char) for char in a]
yield [chr(char) for char in B]

>>l = letters()
l.next()

['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']

but my psychic ability guessed that you actually wanted this instead:
def letters():
a = xrange(ord('a'), ord('z') + 1)
B = xrange(ord('A'), ord('Z') + 1)
a = [chr(char) for char in a]
B = [chr(char) for char in B]
index = 0
while index < 26:
yield a[index]
yield B[index]
index += 1

>>l = letters()
l.next()

'a'

or possibly in a more pythonic style, using for:

def letters():
a = xrange(ord('a'), ord('z') + 1)
B = xrange(ord('A'), ord('Z') + 1)
for lower, upper in zip(a, B):
yield chr(lower)
yield chr(upper)

>>l = letters()
l.next()

'a'

paralelly, my psychic ability also tells me that you might prefer this
instead:

def letters():
a = xrange(ord('a'), ord('z') + 1)
B = xrange(ord('A'), ord('Z') + 1)
for lower, upper in zip(a, B):
yield chr(lower), chr(upper)

>>l = letters()
l.next()

('a', 'A')