Variables in Bash, Perl, Python

Variables: String, array, map summary

Bash variables are untyped, they can be assigned with many types of data. 
1. When assigning values to bash variables, make sure the variables are naked. 
2. However when bash variables are referenced, a '$' in front is needed. 

Perl variables are typed in comparison, and alway need a prefix($, @ or %) no matter whether they are referenced or assigned with values. perl have three basic types:
1. Scalar type, starting with $ such as $myscalar, represents a number or a string of text.
2. Arrays type, starting with @ sign as @myarray, are ordered list of scalar.
3. Hashes type, starting with % sign as %mymap, are unordered list of key value pair.

Python variables don't use any prefix in front, no '$,', no '@' or anything else, they are alway naked. python's main built-in data types are: 
1. Numbers type: including int, long, float, complex.
2. Iterables type
3. Sequence: strings, unicode, lists, tuples.
4. Set: set, frozenset.
5. Mapping(dict)

Tasks:
1.Define three variables for string, array and map respectively.
2.Print the string variable
3.Print the array variable
4.Print the map variable

Bash	Perl	Python
#1.Define three variables for string, array and map respectively. str1="abc"; arr1=("a" "b" "c"); declare -A ass1=([a]=1 [b]=2 [c]=3); #2.Print the string variable echo "$str1"; #3.Print the array variable echo "${arr1[0]}" echo "${arr1[@]}" #4.Print the map variable echo "${ass1[a]}" declare -p ass1 for key in ${!ass1[@]}; do echo -n "$key ${ass1[$key]} " done -------output---------- #1.Define three variables for string, array and map respectively. #2.Print the string variable abc #3.Print the array variable a a b c #4.Print the map variable 1 declare -A ass1='([a]="1" [b]="2" [c]="3" )' a 1 b 2 c 3	#1.Define three variables for string, array and map respectively. $scalar1="abc"; @arr1=("a","b","c"); %hash1=(a=>1,b=>2,c=>3); #2.Print the string variable print "$scalar1\n"; #3.Print the array variable print "@arr1[0]\n"; print "@arr1\n"; #4.Print the map variable print "$hash1{a}\n"; print "@{[%hash1]}\n"; while (($key,$value)=each %hash1) { print "$key $value\n" } -------output---------- #1.Define three variables for string, array and map respectively. #2.Print the string variable abc #3.Print the array variable a a b c #4.Print the map variable 1 c 3 a 1 b 2 c 3 a 1 b 2	#1.Define three variables for string, array and map respectively. str1="abc" list1=["a","b","c"] dict1={"a":1,"b":2,"c":3} #2.Print the string variable print str1 #3.Print the array variable print list1[0] print list1 #4.Print the map variable print dict1['a'] print dict1 for key,value in dict1.items(): print key, value -------output---------- #1.Define three variables for string, array and map respectively. #2.Print the string variable abc #3.Print the array variable a ['a', 'b', 'c'] #4.Print the map variable 1 {'a': 1, 'c': 3, 'b': 2} a 1 c 3 b 2

Bash

Perl

Python

#1.Define three variables for string, array and map respectively.
str1="abc";
arr1=("a" "b" "c");
declare -A ass1=([a]=1 [b]=2 [c]=3);

#2.Print the string variable
echo "$str1";

#3.Print the array variable
echo "${arr1[0]}"
echo "${arr1[@]}"

#4.Print the map variable
echo "${ass1[a]}"
declare -p ass1
for key in ${!ass1[@]}; do 
  echo -n "$key ${ass1[$key]} "
done

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

#1.Define three variables for string, array and map respectively.

#2.Print the string variable
abc

#3.Print the array variable
a
a b c

#4.Print the map variable
1
declare -A ass1='([a]="1" [b]="2" [c]="3" )'
a 1 b 2 c 3

#1.Define three variables for string, array and map respectively.
$scalar1="abc";
@arr1=("a","b","c");
%hash1=(a=>1,b=>2,c=>3);

#2.Print the string variable
print "$scalar1\n";

#3.Print the array variable
print "@arr1[0]\n";
print "@arr1\n";

#4.Print the map variable
print "$hash1{a}\n";
print "@{[%hash1]}\n";
while (($key,$value)=each %hash1) {
    print "$key $value\n"
}

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

#1.Define three variables for string, array and map respectively.

#2.Print the string variable
abc

#3.Print the array variable
a
a b c

#4.Print the map variable
1
c 3 a 1 b 2
c 3
a 1
b 2

#1.Define three variables for string, array and map respectively.
str1="abc"
list1=["a","b","c"]
dict1={"a":1,"b":2,"c":3}

#2.Print the string variable
print str1

#3.Print the array variable
print list1[0]
print list1

#4.Print the map variable
print dict1['a'] 
print dict1
for key,value in dict1.items():
    print key, value

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

#1.Define three variables for string, array and map respectively. 

#2.Print the string variable 
abc

#3.Print the array variable 
a
['a', 'b', 'c']

#4.Print the map variable 
1
{'a': 1, 'c': 3, 'b': 2}
a 1
c 3
b 2

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

Topics about variables

Variables: String, array, map summary