Python truthiness helper mixing strings and booleans illustrates naïve input validation humor

Description

Screenshot of a dark-themed code editor showing two lines of Python with syntax highlighting. Line 1 reads: "def is_truthy(s):" in which the keyword "def" is aqua, the function name "is_truthy" light blue, and parameters white. Line 2 is indented and reads: "return s in ['True', 'true', 'Yes', 'yes', True]" with "return" in yellow, brackets in white, the four string literals in pink, and the bare Boolean literal True in bold cyan. The snippet attempts to decide whether a value should be considered truthy by checking membership in a heterogeneous list that mixes strings and a Boolean, creating an obvious type-comparison pitfall and ignoring other common cases like "1" or different casing. Seasoned developers will recognize this as a code smell demonstrating poor input validation, hidden bugs from type coercion, and the classic need for clearer normalization logic or a mapping table

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Python CodingMistakes CodeSmells BadPractices CodingHumor DeveloperHumor BugFixing CodeQuality SpaghettiCode

Comments

Anonymous ★ Top Pick Our “robust” truthiness check: a list that treats 'yes', 'True', and, thanks to Python’s bool-int equality, the integer 1 as the same flag. Nothing like shipping a feature where page views accidentally enable production mode

Anonymous ★ Top Pick

Our “robust” truthiness check: a list that treats 'yes', 'True', and, thanks to Python’s bool-int equality, the integer 1 as the same flag. Nothing like shipping a feature where page views accidentally enable production mode
Anonymous

After 20 years in tech, I've learned that 'boolean' is just a suggestion - it's really a string enum with infinite possible values, each client having their own creative interpretation of what constitutes 'true'
Anonymous

Ah yes, the classic 'is_truthy' function that returns True when you pass it the string 'True' but False when you pass it the string 'False' - because apparently we're still debugging that YAML parser from 2015 where everything became a string. This is what happens when your API accepts form data, JSON, and carrier pigeons all through the same endpoint, and you've given up on type hints because 'Python is dynamically typed anyway.' Bonus points: this will fail spectacularly when someone inevitably passes 'TRUE', '1', or 'y', leading to a 3 AM incident where the root cause is 'case sensitivity in boolean string parsing' - a phrase that should never exist in production code but somehow always does
Anonymous

Accepts 'True', 'Yes', and - thanks to bool==int - the number 1; enjoy your retries=1 query param enabling the production feature flag
Anonymous

def is_truthy(s): return s in ['True','true','Yes','yes', True] - when you try to parse booleans and accidentally ship YAML 1.1 semantics; bonus: 1, 1.0, and np.bool_ also count as “yes” because bool is int
Anonymous

Because strict typing is for interviews; prod configs demand diplomatic truth parsing
@koloslolya 3y

What about "y", " Y" and "why not?" ?
@korlivan 3y

What about 1?
1. @choke_hazard 3y
  
  What about sqrt(1) and 1^n?
  
  @HellAbyss 3y
  
  What about ln(e) and -cos(pi)?
  
  @NevermindExpress 3y
  
  What about f(x)=1?
  
  @unknown24907 3y
  
  =1
  
  @gizlu 3y
  
  if(eval(s) in [1,....
  
  @callofvoid0 3y
  
  eval is dangerous
  
  @gizlu 3y
  
  No shit
  
  @SamsonovAnton 3y
  
  eval is evil.
  
  @ZgGPuo8dZef58K6hxxGVj3Z2 3y
  
  Nah man you are wrong just use it properly: eval(“(()=>{ usrNm = \”” + document.getElementById(“usernamebox”).Text + “\”;})();”);
@choke_hazard 3y

I'm pretty sure we also need a byte array/hash of this image
@unknown24907 3y

where are 1,2,…
@unknown24907 3y

it is not haskell
1. @callofvoid0 3y
  
  python
  
  @unknown24907 3y
  
  there is no laziness
  
  @callofvoid0 3y
  
  and by this term what are we tryna result in?
@SamsonovAnton 3y

Hey, what about everything that is not zero/null?
1. @M4lenov 3y
  
  Maybe "No" is not truthy
  
  @SamsonovAnton 3y
  
  You say that to char No[] = "No"; printf("%s\n", (No ? "Yes!" : "Oh no!")); 😝
@realVitShadyTV 3y

What about stop using this shitty lang for dumb nerds?
@ZgGPuo8dZef58K6hxxGVj3Z2 3y

What about sqrt(a*a+a*a)?
@affirvega 3y

yaml be like
𝙳𝚖𝚢𝚝𝚛𝚘 𝙼𝚒𝚗𝚝𝚎𝚗𝚔𝚘 3y

it says perhaps in Ukrainian
1. @pavloalpha 3y
  
  Perhaps...
@kaitodev 3y

What about !0 ?

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Python truthiness helper mixing strings and booleans illustrates naïve input validation humor

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