Python Try Catch Block inside lambda

Question

Is it possible to use try catch block inside of a lambda function. I need the lambda function to convert a certain variable into an integer, but not all of the values will be able to be converted into integers.

Answer 1

Nope. A Python lambda can only be a single expression. Use a named function.

It is convenient to write a generic function for converting types:

def tryconvert(value, default, *types):     for t in types:         try:             return t(value)         except (ValueError, TypeError):             continue     return default 

Then you can write your lambda:

lambda v: tryconvert(v, 0, int) 

You could also write tryconvert() so it returns a function that takes the value to be converted; then you don't need the lambda:

def tryconvert(default, *types):     def convert(value):         for t in types:             try:                 return t(value)             except (ValueError, TypeError):                 continue         return default     # set name of conversion function to something more useful     namext = ("_%s_" % default) + "_".join(t.__name__ for t in types)     if hasattr(convert, "__qualname__"): convert.__qualname__ += namext     convert.__name__ += namext     return convert 

Now tryconvert(0, int) returns a function convert_0_int that takes a value and converts it to an integer, and returns 0 if this can't be done. You can use this function right away (not saving a copy):

mynumber = tryconert(0, int)(value) 

Or save it to call it later:

intconvert = tryconvert(0, int) # later... mynumber = intconvert(value)