Python lambda function printing <function <lambda> at 0x7fcbbc740668> instead of value

问题

I am a beginner in python, and I was playing around with lambda functions. I was writing a program using lambda function to print characters that are +1 the ascii value of the input characters. My code is

#!/usr/bin/python
import sys
try:
  word = sys.argv[1]
except:
  print "No arguments passed"
  sys.exit(1)

def convert_ascii(char):
  return  "".join(chr(ord(char) + 1))

for i in word:
  print convert_ascii(i)
  print lambda x: chr(ord(i) + 1)

I have a function convert_ascii that does the same thing as lambda. However, my output is

/usr/bin/python2.7 /home/user1/PycharmProjects/test/Tut1/asciipl2.py "abc def ghi"
b
<function <lambda> at 0x7f0310160668>
c
<function <lambda> at 0x7f0310160668>
d
<function <lambda> at 0x7f0310160668>
!
<function <lambda> at 0x7f0310160668>
e
<function <lambda> at 0x7f0310160668>
f
<function <lambda> at 0x7f0310160668>
g
<function <lambda> at 0x7f0310160668>
!
<function <lambda> at 0x7f0310160668>
h
<function <lambda> at 0x7f0310160668>
i
<function <lambda> at 0x7f0310160668>
j
<function <lambda> at 0x7f0310160668>

The purpose of this script is learning lambda, though there are other ways to do this program. Please let me know what am I doing wrong. Process finished with exit code 0

回答1:

You aren't calling the function. It's the same as if you wrote print convert_ascii instead of print convert_ascii(i).

Try

print (lambda x: chr(ord(x) + 1))(i)

Note that I changed ord(i) to ord(x) in the function body.

回答2:

Currently you are printing a function object. You have to call the function.

Receive the function in a variable and call it with a parameter.

for i in word:
  print convert_ascii(i)
  fun=lambda x: chr(ord(x) + 1)
  print fun(some_arg) 

回答3:

The Lambda Keyword returns an anonymous function:

>>> func = lambda x: x+1
>>> print(func)
<function <lambda> at 0x7f0310160668>

the above is (not counting behing-the-scenes magic) equivalent to:

>>> def func(x):
        return x+1

>>> print(func)
<function func at 0x7fa73d3e6bf8>

to invoke the function, lambda or not, you still have to call it:

>>> print(func)
<function <lambda> at 0x7f0310160668>
>>> func(123)
124

That said, Lambdas are not very well suited to this situation, and are better used if a function or construct requires a short function.

>>> word = "spam"
>>> map(lamda x: chr(ord(x) + 1), word)

回答4:

You are trying to print the function itself. Instead of that, assign the function in a variable, and pass the parameter to the variable, or use the same within print itself.

for i in word:
  z = lambda x: chr(ord(x) + 1)
  print z(i)

or

for i in word:
  print (lambda x: chr(ord(x) + 1))(i)

or to learn map, you can use map to get the same result

for i in word:
  print "".join(map(lambda x: chr(ord(x) + 1), i))

来源：https://stackoverflow.com/questions/32670130/python-lambda-function-printing-function-lambda-at-0x7fcbbc740668-instead-of