converts an input sqlite sql file into the format used by https://dbdiagram.io/

sqlitetodbdiagram.py

import re

text = ""
output = ""
with open("input.sql") as f:
    text = f.read()

text = re.sub(r"--.*", "", text)

for m_table in re.finditer(r"CREATE\s+TABLE\s+IF\s+NOT\s+EXISTS\s+"\
                           "(\w+)\s+\(([\s\S]+?)\);", text):
    output += "Table {} ".format(m_table.group(1)) + "{\n"

    for m_attr in re.finditer(r"(\w+)\s+(INTEGER|REAL|TEXT|BLOB)"\
                              "((?:\s*(?:PRIMARY KEY|NOT NULL|UNIQUE))*)",
                              m_table.group(2)):
        output += " "*4 + m_attr.group(1) + " " + m_attr.group(2)
        modifiers = m_attr.group(3).strip()
        if len(modifiers)>0:
            output += " [" + re.sub(r"PRIMARY KEY|NOT NULL|UNIQUE",
                                    "\g<0>,", modifiers)[:-1] + "]"
        output += "\n"

    output += "}\n"

    for m_fk in re.finditer(r"FOREIGN KEY\s*\((\w+)\)"\
                            "\s*REFERENCES\s+(\w+)\s*\((\w+)\)",
                            m_table.group(2)):
        output += "Ref: {}.{} > {}.{}\n".format(m_table.group(1),
                          m_fk.group(1),
                          m_fk.group(2),
                          m_fk.group(3))

    output += "\n"
    

print(output)
with open("output.sql", "w") as f:
    f.write(output)