elif: SyntaxError: invalid syntax-CodePudding

I want to re.search within an if statement but regardless of identation, get syntax error. Is it because elif: has no condition?

    fr = re.compile(r'(long_regex)', flags = re.DOTALL | re.MULTILINE)
    fra = fr.search(text)
    if fra:
        result = fra.group(5)
    elif:
        f3 = re.compile(r'(some_regex_1)', flags = re.DOTALL | re.MULTILINE)
        fr3 = f3.search(text)
        result = fr3.group(5)
    elif:
        f4 = re.compile(r'(some_regex)', flags = re.DOTALL | re.MULTILINE)
        fr4 = f4.search(text)
        result = fr4.group(4)
    else:
        result = None

error message

  Input In [102]
    elif:
        ^
SyntaxError: invalid syntax

CodePudding user response：

In elif you have if, it requires a condition and you provide none, it should be

if condition1:
    pass
elif condition2:
    pass

Using walrus operator (since py3.8) you can improve your code to look like

if fra := re.search(r'(long_regex)', text, flags=re.DOTALL | re.MULTILINE):
    result = fra.group(5)
elif fr3 := re.search(r'(some_regex_1)', text, flags=re.DOTALL | re.MULTILINE):
    result = fr3.group(5)
elif fr4 := re.search(r'(some_regex)', text, flags=re.DOTALL | re.MULTILINE):
    result = fr4.group(4)
else:
    result = None

If the code is executed multiple times, it should be better to compile the regex onces

Define the compiled regex globally in the file

F2 = re.compile(r'(long_regex)', flags=re.DOTALL | re.MULTILINE)
F3 = re.compile(r'(some_regex_1)', flags=re.DOTALL | re.MULTILINE)
F4 = re.compile(r'(some_regex)', flags=re.DOTALL | re.MULTILINE)

Then use it in your methods

if fra := F2.search(text):
    result = fra.group(5)
elif fr3 := F3.search(text):
    result = fr3.group(5)
elif fr4 := F4.search(text):
    result = fr4.group(4)
else:
    result = None

CodePudding user response：

For elif statement you must provide the condition. For example:

if a == 1:
  do_a()
elif a == 2:
  do_b()
else:
  do_c()