Coding Bash vs. Perl vs. Python (by Evan Liu)

#1.Create a map
#  use associative array as map in Bash 4
declare -A ages
ages=([dad]=42 [mom]=40 [me]=7)

#2.Print all the item in the map
declare -p ages


-------output----------

#1.Create a map
#  use associative array as map in Bash 4

#2.Print all the item in the map
declare -A ages='([mom]="40" [dad]="42" [me]="7" )'

#1.Create a map
%ages1=(dad=>42,mom=>40,me=>7);
#  or use array to define
%ages2=("dad",42,"mom",40,"me",7);
#  or use qw()
%ages3=qw(dad 42 mom 48 me 7);

#2.Print all the item in the map
#  use [] to get the reference to array
print "@{[%ages1]}\n";
#  or use () to change to array
print join(" ", (%ages2))."\n";
#  or
print join(" ",%ages3)."\n";

-------output----------

#1.Create a map
#  or use array to define
#  or use qw()

#2.Print all the item in the map
#  use [] to get the reference to array
mom 40 me 7 dad 42
#  or use () to change to array
dad 42 me 7 mom 40
#  or
dad 42 me 7 mom 48

#1.Create a map
#  use dictionary as map
ages={'dad':42,'mom':48,'me':7}

#2.Print all the item in the map
print ages
print ages.items()


-------output----------

#1.Create a map 
#  use dictionary as map 

#2.Print all the item in the map 
{'dad': 42, 'me': 7, 'mom': 48}
[('dad', 42), ('me', 7), ('mom', 48)]

#1.Create a map
declare -A ages=([dad]=42 [mom]=40 [me]=7)

#2.Print all the keys and values in the map
echo ${!ages[@]} 
echo ${ages[@]}

-------output----------

#1.Create a map

#2.Print all the keys and values in the map
mom dad me
40 42 7

#1.Create a map
%ages=(dad=>42,mom=>40,me=>7);

#2.Print all the keys and values in the map
print join(" ", keys %ages)."\n";
print join(" ", values %ages)."\n";

-------output----------

#1.Create a map

#2.Print all the keys and values in the map
mom me dad
40 7 42

#1.Create a map
ages={'dad':42,'mom':48,'me':7}

#2.Print all the keys and values in the map
print ages.keys()
print ages.values()


-------output----------

#1.Create a map 

#2.Print all the keys and values in the map 
['dad', 'me', 'mom']
[42, 7, 48]

#1.Create a map
declare -A ages=([dad]=42 [mom]=40 [me]=7)

#2.Lookup a key in the map
echo ${ages[me]}

-------output----------

#1.Create a map

#2.Lookup a key in the map
7

#1.Create a map
%ages=(dad=>42,mom=>40,me=>7);

#2.Lookup a key in the map
print $ages{"me"};

-------output----------

#1.Create a map

#2.Lookup a key in the map
7

#1.Create a map
ages={'dad':42,'mom':48,'me':7}

#2.Lookup a key in the map
print ages['me']

-------output----------

#1.Create a map 

#2.Lookup a key in the map 
7

#1.Create a map
declare -A ages=([dad]=42 [mom]=40 [me]=7)

#2.Iterate over the map
for key in ${!ages[@]}; do 
  echo "$key ${ages[$key]}"
done

-------output----------

#1.Create a map

#2.Iterate over the map
mom 40
dad 42
me 7

#1.Create a map
%ages=(dad=>42,mom=>40,me=>7);

#2.Iterate over the map
#  use foreach
foreach $key (keys %ages){print "$key $ages{$key}\n"}
#  or use while
while (($key,$value)=each(%ages)){print "$key $value\n"}

-------output----------

#1.Create a map

#2.Iterate over the map
#  use foreach
me 7
dad 42
mom 40
#  or use while
me 7
dad 42
mom 40

#1.Create a map
ages={'dad':42,'mom':48,'me':7}

#2.Iterate over the map
for key in ages:
    print key, ages[key]
#  or
for key,value in ages.items():
    print key, value


-------output----------

#1.Create a map 

#2.Iterate over the map 
dad 42
me 7
mom 48
#  or 
dad 42
me 7
mom 48

#1.Create a map
declare -A ages=([dad]=42 [mom]=40 [me]=7)

#2.Remove the element  with the key of 'me'
unset ages[me]
declare -p ages

-------output----------

#1.Create a map

#2.Remove the element  with the key of 'me'
declare -A ages='([mom]="40" [dad]="42" )'

#1.Create a map
%ages=(dad=>42,mom=>40,me=>7);

#2.Remove the element  with the key of 'me'
delete $ages{me};
print join(' ', %ages);


-------output----------

#1.Create a map

#2.Remove the element  with the key of 'me'
mom 40 dad 42

#1.Create a map
ages={'dad':42,'mom':48,'me':7}

#2.Remove the element  with the key of 'me'
del ages['me']
print ages.items()

-------output----------

#1.Create a map 

#2.Remove the element  with the key of 'me' 
[('dad', 42), ('mom', 48)]

#1.Create a map
declare -A ages=([dad]=42 [mom]=40 [me]=7)
declare -p ages

#2.Clear the map
ages=()
[[ "${ages[@]}" ]] && declare -p ages || echo "ages not defined or empty"
#  or use unset
declare -A ages=([dad]=42 [mom]=40 [me]=7)
unset ages
[[ "${ages[@]}" ]] && declare -p ages || echo "ages not defined or empty"

-------output----------

#1.Create a map
declare -A ages='([mom]="40" [dad]="42" [me]="7" )'

#2.Clear the map
ages not defined or empty
#  or use unset
ages not defined or empty

#1.Create a map
%ages=(dad=>42,mom=>40,me=>7);
print join(' ', %ages)."\n";

#2.Clear the map
%ages=();
#  do not use defined(%ages1), which is only for scalar
print %ages? %ages: "ages not defined or empty\n";
#  or use undef
undef %ages;
print %ages? %ages: "ages not defined or empty\n";


-------output----------

#1.Create a map
mom 40 dad 42 me 7

#2.Clear the map
#  do not use defined(%ages1), which is only for scalar
ages not defined or empty
#  or use undef
ages not defined or empty

#1.Create a map
ages={'dad':42,'mom':48,'me':7}
print ages

#2.Clear the map
ages.clear()
print ages if 'ages' in locals() else "ages not defined"
#  or use del
del ages
print ages if 'ages' in locals() else "ages not defined"

-------output----------

#1.Create a map 
{'dad': 42, 'me': 7, 'mom': 48}

#2.Clear the map 
{}
#  or use del 
ages not defined