Python腳本：text = "abcde"print("text[::-1] : ", text[::-1])print("text[5:0:-1] : ", text[5:0:-1])輸出：text[::-1] : edcbatext[5:0:-1] : edcb可以定義一個自定義函數來避免輸入重復嗎？例如：text = "abcde"def fuc(x): print(x, ":", x) fuc(text[::-1])fuc(text[5:0:-1])要求。輸出：text[::-1] : edcbatext[5:0:-1] : edcb
2 回答
慕哥6287543
TA貢獻1831條經驗 獲得超10個贊
使用 f 字符串可以實現涉及字符串插值的解決方案。但是，f 字符串僅適用于 Python 3.8+
但是，我們可以很容易地實現字符串插值，如如何在 Python 中實現字符串插值
Current Modification 擴展了上述參考，以允許除了變量查找之外的表達式。
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
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