Python:打印函数文本的自定义打印函数

Question

Python script：

text = "abcde"
print("text[::-1] : ", text[::-1])
print("text[5:0:-1] : ", text[5:0:-1])

输出：

text[::-1] :  edcba
text[5:0:-1] :  edcb

是否可以定义一个自定义函数来避免键入中的重复性？ 例如：

text = "abcde"
def fuc(x):
print(x, ":", x)

fuc(text[::-1])
fuc(text[5:0:-1])

要求输出：

text[::-1] :  edcba
text[5:0:-1] :  edcb

Answer 1

在python 3.8+中，你可以使用自我记录表达式

>>> print(f"{a[::-1]=}") 
a[::-1]='edcba'

Answer 2

使用 f 字符串可以解决涉及字符串插值的解决方案。 但是，f字符串仅适用于Python 3.8+。

但是，我们可以很容易地实现字符串插值，如如何在 Python 中实现字符串插值中所述

"当前修改"扩展了上述引用，以允许除变量查找之外的表达式。

import sys
from re import sub
def interp(s):
'''Implement simple string interpolation to handle
"{var}" replaces var with its value from locals
"{var=}" replaces var= with var=value, where value is the value of var from locals
"{expressions} use eval to evaluate expressions (make eval safe by only allowing items from local functions and variables in expression'''
# 1. Implement self-documenting expressions similar to https://docs.python.org/3/whatsnew/3.8.html#f-strings-support-for-self-documenting-expressions-and-debugging
s1 = sub( r'{s*(.*?)=s*}', lambda m: m.group(1) + '=' + '{' + m.group(1) + '}', s)
# Get the locals from the previous frame
previous_frame = sys._getframe(1)  # i.e. current frame(0), previous is frame(1)
d = previous_frame.f_locals        # get locals from previous frame
# 2--Replace variable and expression with values
# Use technique from http://lybniz2.sourceforge.net/safeeval.html to limit eval to make it safe
# by only allowing locals from d and no globals
s2 = sub(r'{s*([^s]+)s*}', lambda m: str(d[m.group(1)]) if m.group(1) in d else str(eval(m.group(1), {}, d)), s1)
return s2
# Test
a = "abcde"
print(interp("a has value {a}"))  # without self-doc =
#Output>>> a has value abcde
print(interp("{a[::-1]=}"))       # with self-doc =
#Output>>> a[::-1]=edcba
print(interp('{a[4:0:-1]=}'))     # with self-doc =
#Output>>> a[4:0:-1]=edcb
print(interp('sum {1+1}') # without self-doc =
#Output>>> sum 2
print(interp('{1+1=}'))  # with self-doc =
#Output>>> 1+1=2