Ideaz From Ur Brainz

In the following code snippet, 'c' is not as key in 'foo' but is set to {} when the last check for foo->c->0 is called. / tmp ( ) $ cat foo . pl use strict ; use warnings ; use Data : : Dumper ; sub abcde { my $foo = { 'a' = > 1 , 'b' = > 2 } ; print Dumper ( $foo ) ; if ( exists $foo - > { c } & & defined $foo - > { c } - > { 0 } ) { print "C is defined" ; } print Dumper ( $foo ) ; if ( defined $foo - > { c } and defined $foo - > { c } - > { 0 } ) { print "C is defined" ; } print Dumper ( $foo ) ; if ( defined $foo - > { c } - > { 0 } ) { print "C is defined" ; } print Dumper ( $foo ) ; } abcde ( ) ; / tmp ( ) $ perl foo . pl $VAR1 = { 'a' = > 1 , 'b' = > 2 } ; $VAR1 = { 'a' = > 1 , ...

waitall() method in eventlet.GreenPool doesn't raise exceptions but just logs them, whereas in case of wait on the greenthread returned by spawn from evenlet.GreenPool raises the exception. # cat foo . py import eventlet pool = eventlet . GreenPool ( 1 ) def foo ( ) : raise ValueError gt = pool . spawn ( foo ) try: pool . waitall ( ) except Exception , e : print " pool.waitall Exception raised: %r " % e try: gt . wait ( ) except Exception , e : print " gt.wait() Exception raised: %r " % e # python foo . py Traceback ( most recent call last ) : File " /usr/lib/python2.7/site-packages/eventlet/hubs/hub.py " , line 346 , in fire_timers timer ( ) File " /usr/lib/python2.7/site-packages/eventlet/hubs/timer.py " , line 56 , in __call__ cb ( * args , * * kw ) File " /usr/lib/python2.7/site-packages/eventlet/greenthread.py " , line 194 , in main result = functi...

>>> for e in ( 0 , "0" , None , "None" , 1.23 , "1.23" , [ 1 , 2 ], { "foo" : "bar" }): ... print " %r " % e ... 0 '0' None 'None' 1.23 '1.23' [ 1 , 2 ] { 'foo' : 'bar' } When %s is used to interpolate to string there could be a bit of ambiguity introduced. >>> for e in ( 0 , "0" , None , "None" , 1.23 , "1.23" , [ 1 , 2 ], { "foo" : "bar" }): ... print " %s " % e ... 0 0 None None 1.23 1.23 [ 1 , 2 ] { 'foo' : 'bar' }

/ tmp ( ) $ cat out_err_redirect_test . sh echo message to stdout echo message to stderr > & 2 / tmp ( ) $ bash out_err_redirect_test . sh message to stdout message to stderr # Message to stdout is redirected to dev null / tmp ( ) $ bash out_err_redirect_test . sh > / dev / null message to stderr # Message to stderr is redirected to dev null / tmp ( ) $ bash out_err_redirect_test . sh 2 > / dev / null message to stdout # Message to stderr and stdout is redirected to dev null / tmp ( ) $ bash out_err_redirect_test . sh > / dev / null 2 > / dev / null # Messaged to stdout is redirected to dev null , and stderr to configured stdout ( implies dev null ) / tmp ( ) $ bash out_err_redirect_test . sh > / dev / null 2 > & 1 # Message to stderr is redirected to stdout ( screen ) and stdout to dev null / tmp ( ) $ bash out_err_redirect_test . sh 2 > & 1 > / dev / null message to stderr

Below the tuple (1, 2, 3) is getting expanded as 3 arguments and the format representation is expecting to have 3 %s or %r to be printed, > > > print " %r " % ( 1 , 2 , 3 ) Traceback ( most recent call last ) : File " <stdin> " , line 1 , in < module > TypeError: not all arguments converted during string formatting > > > print " %s " % ( 1 , 2 , 3 ) Traceback ( most recent call last ) : File " <stdin> " , line 1 , in < module > TypeError: not all arguments converted during string formatting > > > print " %s " % str ( ( 1 , 2 , 3 ) ) ( 1 , 2 , 3 )

Perl looping of an array with index as well as the item stored in variables, /tmp$ cat loop_with_index.pl  my @arr=(1,2,3,4); while (my ($i, $x) = each(@arr)) {     print "$i: $x\n"; } /tmp$ perl loop_with_index.pl  0: 1 1: 2 2: 3 3: 4

To get the keys of a constant hashref you first need to learn that a constant is actually a function and hence use () to get the keys from it INPUT: $ cat perlConstant.pl use Data::Dumper; use constant FOOHASH => { "foo" => "bar", }; print FOOHASH->{"foo"}."\n"; foreach $key (keys %{FOOHASH()}) { FOOHASH->{$key} = "bar1"; } print FOOHASH->{"foo"}."\n"; foreach $key (keys %{FOOHASH}) { FOOHASH->{$key} = "bar2"; } print FOOHASH->{"foo"}."\n"; OUTPUT: $ perl perlConstant.pl bar bar1 bar1