Python unable to find variable when concatenating two strings

Question

This seems like an incredibly silly problem, but it's doing my nut in. I just started working with Python a few days ago, after spending a while in other languages, and I've run into a very weird problem. I'm attempting to set a top-level string variable called 'word' to the concatenation of itself and a letter. Python is able to find the variable just fine, as demonstrated below.

statement of "word = letter"

However, any time I try to concatenate, I suddenly get an error telling me Python is unable to find the variable.

statements of "word += letter" and "word = word + letter"

The yellow squiggle is my IDE telling me that the variable can't be found. I've tried literally directly copy+pasting other solutions from other stack-exchange posts. It's a little embarrassing to be having this much trouble with concatenation, but I've tried most of the stuff I can think of.

Edit:Here's my code. As you can see, "word" is initialized at the top of the file:


word_dict = PyDictionary()
repeats = 5
word = "e"



 def handle_input(x, y, letter): 
    word += letter

    print(word)

    coords = make_coords(x, y)
    for list in grid:
        for button in list:
           button.update(disabled=True)
    for coord in coords:
        x = coord[0]
        y = coord[1]
        list = grid[y]
        button = list[x]
        button.update(disabled=False)

Can you just copy and paste your code (including initializations of variable) into the post instead of using screenshots? — Aniketh Malyala, Aug 11 '21 at 22:00
Did you define the variable earlier, like before you try to do `word = letter` or `word += letter`? — Daniyal Warraich, Aug 11 '21 at 22:00
Did you *initialize* `word` before trying to use `word += letter`? — chepner, Aug 11 '21 at 22:00
`foo += "bar"`: now tell me the value of `foo` without knowing the value of `foo` to begin with. — chepner, Aug 11 '21 at 22:01
Can you show the specific part of your code thats giving the error (just initialization of variables and where the error is coming)? — Aniketh Malyala, Aug 11 '21 at 22:03
Try using `global word` at the top of the function that changes `word`. — Daniyal Warraich, Aug 11 '21 at 22:06
I think this is a duplicate of https://stackoverflow.com/questions/370357/unboundlocalerror-on-local-variable-when-reassigned-after-first-use — mkrieger1, Aug 11 '21 at 22:08
@DaniyalWarraich The IDE (PyLance I assume) is throwing a warning. UnboundLocalError would only occur at runtime — OneCricketeer, Aug 11 '21 at 22:10
Does this answer your question? [Using global variables in a function](https://stackoverflow.com/questions/423379/using-global-variables-in-a-function) — Woodford, Aug 11 '21 at 22:51

score 3 · Accepted Answer · answered Aug 11 '21 at 22:08

Since your word is defined outside of the function, you need to redeclare it as a global variable:

def handle_input(x, y, letter): 
  global word #add this line
  word += letter

  print(word)

  coords = make_coords(x, y)
  for list in grid:
      for button in list:
          button.update(disabled=True)
  for coord in coords:
      x = coord[0]
      y = coord[1]
      list = grid[y]
      button = list[x]
      button.update(disabled=False)

score 0 · Answer 2 · answered Aug 11 '21 at 22:34

When you defined your variable word outside the function, it became a global variable. Global variables are available from within any scope. So you can use it inside your function, but first you must redeclare it as a global variable inside your function by adding global word at the first line in the function.

def handle_input(x, y, letter): 
    global word

Another solution is to define your variable `word` inside the function so that it is declared as a local variable which can be accessible only in that function.

def handle_input(x, y, letter): 
    word = "e"

Python unable to find variable when concatenating two strings

2 Answers2