python lambda expression in multiple lines.

pip install git+https://github.com/likianta/lambda-ex

note: it requires python 3.8+.

from lambda_ex import xlambda

add = xlambda('a, b', """
    return a + b
""")

print(add(1, 2))  # -> 3

from lambda_ex import xlambda

add = xlambda('a, b, c=0', """
    return a + b + c
""")

print(add(1, 2))  # -> 3
print(add(1, 2, 3))  # -> 6
print(add(a=1, b=2, c=3))  # -> 6

if you are passing a complex object, for example a long list, you can also use "post" kwargs like below:

from lambda_ex import xlambda

print_names = xlambda('title_case=False', """
    for n in names:
        if title_case:
            print(n.title())
        else:
            print(n)
""", kwargs={
    'names': (
        'anne',
        'bob',
        'charlie',
        'david',
        'erin',
    )
})

print_names(title_case=True)
#   -> Anne
#      Bob
#      Charlie
#      David
#      Erin
print_names(title_case=True, names=('fred', 'george', 'harry'))
#   -> Fred
#      George
#      Harry

from lambda_ex import xlambda

add = xlambda('a: int, b: int', """
    return a + b
""")

print(add(1, 2))  # -> 3

use __selfunc__ to call itself:

from lambda_ex import xlambda

fibonacci = xlambda(('n'), """
    if n <= 0:
        raise ValueError(n)
    if n <= 2:
        return 1
    return __selfunc__(n - 1) + __selfunc__(n - 2)
""")

fibonacci(10)  # -> 55

lambda-ex can directly access locals and globals in its occurrence:

from lambda_ex import xlambda

a = 1
b = 2

add = xlambda('', """
    return a + b
""")

add()  # -> 3

and modify "global" values:

from lambda_ex import xlambda

a = 1
b = 2
c = 0

add = xlambda('', """
    global c
    c = 3
    return a + b + c
""")

print(add())  # -> 6
print(a, b, c)  # -> 1 2 3

warning: there is some limitation in this case, see here.

• please check examples folder to get more usages.

• if you're using pycharm, you can add a code template to pycharm's live template:

  xlambda('$END$', """
  
  """)
  

  

• by default lambda-ex inherits caller context, if you want to forbid this (it would be little faster then), set inherit_context to False:

  from lambda_ex import xlambda
  hello_world = xlambda('', """
      print('hello world')
  """, inherit_context=False)

• use \\n instead of \n in your lambda expression. or you may use the r-string (example below).

  from lambda_ex import xlambda
  foo = xlambda('', r"""
      print('one\ntwo\nthree')
  """)
  foo()

• you can only use global when xlambda in top module, otherwise it won't affect outside variables:

  from lambda_ex import xlambda
  
  def foo():
      a = 1
      b = 2
      c = 0
  
      add = xlambda('', """
          global c  # no effect
          # btw do never use `nonlocals ...` in xlambda, it will raise an
          #   error at once.
          c = 3
          return a + b + c
      """)
  
      print(add())  # -> 6
      print(a, b, c)  # -> 1 2 0
      #                        ^ no change
  
  foo()