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Regex Substitution

1、题目描述

The re.sub() tool (sub stands for substitution) evaluates a pattern and, for each valid match, it calls a method (or lambda). The method is called for all matches and can be used to modify strings in different ways. The re.sub() method returns the modified string as an output.

Learn more about re.sub().

Transformation of Strings

Code

import re

#Squaring numbers
def square(match):
    number = int(match.group(0))
    return str(number**2)

print re.sub(r"\d+", square, "1 2 3 4 5 6 7 8 9")

Output

1 4 9 16 25 36 49 64 81

Replacements in Strings

Code

import re

html = """
<head>
<title>HTML</title>
</head>
<object type="application/x-flash" 
  data="your-file.swf" 
  width="0" height="0">
  <!-- <param name="movie"  value="your-file.swf" /> -->
  <param name="quality" value="high"/>
</object>
"""

print re.sub("(<!--.*?-->)", "", html) #remove comment

Output

<head>
<title>HTML</title>
</head>
<object type="application/x-flash" 
  data="your-file.swf" 
  width="0" height="0">

  <param name="quality" value="high"/>
</object>

Task

You are given a text of N lines. The text contains && and || symbols.

Your task is to modify those symbols to the following:

&& → and
|| → or

Both && and || should have a space " " on both sides.

Input Format

The first line contains the integer, N . The next N lines each contain a line of the text.

Constraints

0<N<100

Neither && nor || occur in the start or end of each line.

Output Format

Output the modified text.

Sample Input

11
a = 1;
b = input();

if a + b > 0 && a - b < 0:
    start()
elif a*b > 10 || a/b < 1:
    stop()
print set(list(a)) | set(list(b)) 
#Note do not change &&& or ||| or & or |
#Only change those '&&' which have space on both sides.
#Only change those '|| which have space on both sides.

Sample Output

a = 1;
b = input();

if a + b > 0 and a - b < 0:
    start()
elif a*b > 10 or a/b < 1:
    stop()
print set(list(a)) | set(list(b)) 
#Note do not change &&& or ||| or & or |
#Only change those '&&' which have space on both sides.
#Only change those '|| which have space on both sides.    

2、解题思路

  • 使用python的正则表达式实现
  • 使用字符串替换实现(替换两次)
# Enter your code here. Read input from STDIN. Print output to STDOUT

import re

lines = int(input().strip())
pattern = r"(?<= )(&&|\|\|)(?= )"
for _ in range(lines):
    print(re.sub(pattern, lambda v: "and" if v.group() == "&&" else "or", input()))
# Enter your code here. Read input from STDIN. Print output to STDOUT

lines = int(input().strip())
for _ in range(lines):
    print(input().replace(" && ", " and ").replace(" && ", " and ").replace(" || ", " or ").replace(" || ", " or "))