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Main Differences Python and SPSS Syntax

Python is Fully Case Sensitive

Experienced SPSS users probably know that SPSS syntax is mostly case insensitive: it doesn't usually matter whether you write syntax in lower case, upper case or a mixture of these. Like so, the FREQUENCIES commands below are all equivalent.

*SPSS SYNTAX IS MOSTLY CASE INSENSITIVE.

FREQUENCIES V01 TO V10.

frequencies v01 to v10.

fReQuEnCiEs v01 tO V10.

In contrast, Python is fully case sensitive. As a consequence, you always need to use the exact right casing in Python or you may otherwise trigger a wide variety of errors and warnings.

*PYTHON IS FULLY CASE SENSITIVE.

begin program python3.
myName = 'Ruben'
print(myName) # Ruben
 print(myname) # [...] NameError: name 'myname' is not defined
 end program.

Note that you also need use the correct casing for SPSS variable names in Python. Avoiding all upper case for SPSS variable names tends to simplify things.

Check Object Types in Python

In SPSS, “data types” mostly refer to variable types. Keep in mind that “variables” in SPSS are columns of cells that hold data values. There's only 2 SPSS variable types:

These 2 types determine what you can (not) do with a variable in SPSS. Confusingly, the Type column in variable view suggests that there's many more variable types but these are formats, not types as explained in SPSS Variable Types and Formats.

SPSS String Versus Numeric Variable In Variable View

In Python, we'll also encounter strings and numbers but these are called objects instead of variables and only hold a single value. An entire column of values is usually represented as a Python list object or a Python tuple. And these are different object types than the strings or integers they may contain.

Like so, there's many different Python object types which we briefly cover in Quick Overview Python Object Types. Just as with SPSS variable types, Python object types determine what you can (not) do with them and how. That's why you sometimes need to check what type of object you're dealing with. This is simply done with print(type(myObject)) as shown below.

*FIND WHAT TYPE OF OBJECT YOU'RE DEALING WITH.

begin program python3.
myName = 'Ruben'
print(type(myName)) # <class 'str'>
 end program.

Note: Python users can create new object types known as Classes. Such classes typically have their own methods and properties. You may need a bit of study for dealing with some of them.

Indentation Matters in Python

Basic looping in SPSS is done with

The syntax below briefly illustrates this structure.

*SPSS DO REPEAT EXAMPLE.

do repeat #vars = v01 to v05.
compute #vars = 0.
end repeat.

In Python, the start of a loop is indicated by a for or while statement. After that, the indentation of the lines that follow indicate where a loop ends. The examples below illustrate how this works.

*LOOP OVER 2 PRINT STATEMENTS.

begin program python3.
for ind in range(10):
    print('COMPUTE V{} = {}.'.format(ind,ind))
    print("VARIABLE LABELS V{} 'Mean Job Satisfaction Score'.".format(ind))
end program.

*LOOP OVER 1 PRINT STATEMENT.

begin program python3.
for ind in range(10):
    print('COMPUTE V{} = {}.'.format(ind,ind))
print("VARIABLE LABELS V{} 'Mean Job Satisfaction Score'.".format(ind))
end program.

This means that in order for your Python code to function properly, you must apply the correct indentation levels. This goes for

Note that we cover most of these in Conditions and Loops in Python.

Python Assignment or Comparison Operator

In SPSS syntax, the = operator is used for

The syntax below shows 2 minimal examples.

*USE = FOR ASSIGNMENT IN SPSS.

compute m01 = mean(v01 to v05).

*USE = FOR COMPARISON IN SPSS.

do if (gender = 0).
...
end if.

In contrast, Python uses

The examples below briefly illustrate the difference.

*DIFFERENCE = VERSUS ==.

begin program python3.
myAction = 'PRINT' # = assigns value to object
 if myAction == 'PRINT': # == compares values
         print('FREQUENCIES ALL.')
end program.

For an overview of these and many other Python operators, read up on Python Operators - Quick Overview & Examples.

Escape Sequences in SPSS and Python

In SPSS, we rarely use escape sequences but 2 main exceptions are

Few SPSS users are aware of such escape sequences but running the syntax below nicely illustrates both.

*SET UP EMPTY DATA.

data list free/v01.
begin data.
6
end data.

*ESCAPE SINGLE QUOTE BY DOUBLING IT.

add value labels v01 6 'Don''t know'.

*ESCAPE "n" BY BACKSLASH.

variable labels v01 'This label continues on\nline 2 and\nline 3'.

*SHOW LABELS IN SUCCEEDING OUTPUT TABLES.

set tnumbers both tvars both.

*QUICK CHECK.

frequencies v01.

Result

Escape Sequences In SPSS Output Table

So those are basic escape sequences in SPSS syntax. Now, what about Python?

In Python, escaping is always done with a backslash. A backslash itself is also escaped by a backslash. Alternatively, specify a string as a raw string by preceding it with “r”. The syntax below shows some basic examples.

*ESCAPE SINGLE QUOTE BY BACKSLASH.

begin program python3.
vallab = 'Don\'t know'
print(vallab)
end program.

*ESCAPE BACKSLASH WITH BACKSLASH.

begin program python3.
rDir = 'D:\\analyses_example\\new-data'
print(rDir)
end program.

*ESCAPE BACKSLASH BY RAW STRING.

begin program python3.
rDir = r'D:\analyses_example\new-data'
print(rDir)
end program.

Comments in SPSS and Python

In SPSS we usually comment entire lines of syntax by

In rare cases, we may enter a comment within some command enclosed by /* and */ as shown below.

*THIS ENTIRE LINE IS A COMMENT IN SPSS SYNTAX.

frequencies all /* AND HERE'S A COMMENT WITHIN A COMMAND */
/barchart.

In Python, everything between a hashtag and the end of the line in which it occurs is a comment. Alternatively, enclose a (multiline) comment by triple quotes.

*FROM # THROUGH END OF LINE IS PYTHON COMMENT.

begin program python3.
#FIRST GREET AUDIENCE BEFORE PROCEEDING
print('Hello!') #DONE
end program.

*PYTHON COMMENT BETWEEN TRIPLE SINGLE QUOTES.

begin program python3.
'''
This is a multiline
comment enclosed by
triple single quotes.
'''
print('Hello!')
end program.

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