How to auto indent next line of string

Question

I am trying to make a program using Python that will auto indent the next line of string when it encounters certain characters such as braces.

For example:

public class Example{

--indent--> public static void main (String[]args){

--indent--> System.out.println("Hello");
}
}

I can't seem to grasp what I need to code in order to achieve that.

Any kind of help will be much appreciated!

Look for lines that end in tokens and add spaces in front of all subsequent lines? — wwii, May 16 '20 at 04:29

score 1 · Answer 1 · answered May 16 '20 at 04:41

This is a quick and dirty way to do it. Basically I just loop through the lines of the input string (cppcode) and keep track of the current indentation (tabdepth). When I encounter a brace in the input line I increment the tabdepth up or down, and then add tabdepth number of tabs to the output line.

cppcode = '''
public class Example{

public static void main (String[]args){

System.out.println("Hello");
}
}
'''


tabdepth = 0

for line in cppcode.split("\n"):
    depth_changed = False
    indentedline = ''.join(['\t'*tabdepth, line])
    for c in line:
        if c == '{':
            tabdepth += 1

        elif c == '}':
            tabdepth -= 1
            depth_changed = True

    if depth_changed: 
        indentedline = ''.join(['\t'*tabdepth, line])

    print(indentedline)

I had a similar thought of looping through the input string but I didn't think of keeping track of the indentation, thank you for this insight. — Amber, May 16 '20 at 05:46

score 1 · Accepted Answer · answered May 16 '20 at 04:50

honestly, the exact way you set up your code depends on if you're doing other things to it to "pretty print" it. a rough outline of something could look like this

def pretty(s):
    start = "{"
    end = "}"
    level = 0
    skip_start = False

    for c in s:
        # raise or lower indent level
        if c == start:
            level += 1
        if c == end:
            level -= 1

        if level < 0:
            raise IndentationError("Error Indenting")

        if c == "\n":
            skip_start = True # I'm bad at naming just a flag to mark new lines

        if c.isspace() and skip_start:
            pass #skip whitspace at start of line
        else:
            if skip_start:
                print("\n", "  " * level, end="") #print indent level
                skip_start = False
            print(c, end = "") #print  character

pretty('''
public class Example{



public static void main (String[]args){
if (1==1){
    //do thing
//do other thing
             // weird messed up whitespace
}else{
System.out.println("Hello");
}
}
}
''')

would output

 public class Example{
   public static void main (String[]args){
     if (1==1){
       //do thing
       //do other thing
       // weird messed up whitespace
     }else{
       System.out.println("Hello");
     }
   }
 }

How to auto indent next line of string

2 Answers2