CheckiO 是面向初学者和高级程序员的编码游戏，使用 Python 和 JavaScript 解决棘手的挑战和有趣的任务，从而提高你的编码技能，本博客主要记录自己用 Python 在闯关时的做题思路和实现代码，同时也学习学习其他大神写的代码。
CheckiO 官网：https://checkio.org/
我的 CheckiO 主页：https://py.checkio.org/user/TRHX/
CheckiO 题解系列专栏：https://itrhx.blog.csdn.net/category_9536424.html
CheckiO 所有题解源代码：https://github.com/TRHX/Python-CheckiO-Exercise
题目描述
【First Word (simplified)】：这个是 First Word 任务的简化版本，任务是找到一个字符串中的第一个单词（单词非字母），输入字符串仅包含英文字母和空格，字符串的开头和结尾没有空格。
【链接】：https://py.checkio.org/mission/first-word-simplified/
【输入】：字符串
【输出】：字符串
【前提】：原字符串仅包含大小写字母和空格
【范例】：
first_word("Hello world") == "Hello"
解题思路
以空格为分隔符，用 split() 方法将原字符串进行切片，返回第一个元素即可。
代码实现
def first_word(text: str) -> str:"""returns the first word in a given text."""return text.split( )[0]if __name__ == '__main__':print("Example:")print(first_word("Hello world"))# These "asserts" are used for self-checking and not for an auto-testingassert first_word("Hello world") == "Hello"assert first_word("a word") == "a"assert first_word("hi") == "hi"print("Coding complete? Click 'Check' to earn cool rewards!")
大神解答
大神解答 NO.1
def first_word(text: str) -> str:"""returns the first word in a given text."""import rereturn(re.findall(r'^\w+',text)[0])
大神解答 NO.2
def first_word(text: str) -> str:"""returns the first word in a given text."""try:text.find(' ')return text[0:int(text.index(' '))]except:return text
大神解答 NO.3
import re
def first_word(text: str) -> str:"""returns the first word in a given text."""if " " not in text:return textelse:ans = re.findall(r"\w+",text)ans = ans[0]return ans
大神解答 NO.4
def first_word(text):index = text.find(" ")return text[:index] if index != -1 else text"""
It's worth to look at the performance of different methods under the same predefined conditions.
Let's check runtime of the 4 methods (10000 executions for each) defined below for the next 4 cases:
-a short str which contains space chars: "asdf we"*10;
-a short str which doesn't contain space chars: "asdfawe"*10;
-a long str which contains space chars: "asdf we"*100000;
-a long str which doesn't contain space chars: "asdf we"*100000.
############################################################################################################
from timeit import timeit as tdef first_word_1(text):return text.split(" ")[0]print(t('first_word_1(x)', setup='x = "asdf we"*10', number=10000, globals=globals())) # ~11.7 ms
print(t('first_word_1(x)', setup='x = "asdfawe"*10', number=10000, globals=globals())) # ~6.1 ms
print(t('first_word_1(x)', setup='x = "asdf we"*100000', number=10000, globals=globals())) # ~90928.2 ms
print(t('first_word_1(x)', setup='x = "asdfawe"*100000', number=10000, globals=globals())) # ~5562.9 msdef first_word_2(text):index = text.find(" ")return text[:index] if index != -1 else textprint(t('first_word_2(x)', setup='x = "asdf we"*10', number=10000, globals=globals())) # ~6.3 ms
print(t('first_word_2(x)', setup='x = "asdfawe"*10', number=10000, globals=globals())) # ~4.7 ms
print(t('first_word_2(x)', setup='x = "asdf we"*100000', number=10000, globals=globals())) # ~7.0 ms
print(t('first_word_2(x)', setup='x = "asdfawe"*100000', number=10000, globals=globals())) # ~2108.4 msdef first_word_3(text):try:index = text.index(" ")return text[:index]except ValueError:return textprint(t('first_word_3(x)', setup='x = "asdf we"*10', number=10000, globals=globals())) # ~5.8 ms
print(t('first_word_3(x)', setup='x = "asdfawe"*10', number=10000, globals=globals())) # ~8.5 ms
print(t('first_word_3(x)', setup='x = "asdf we"*100000', number=10000, globals=globals())) # ~5.8 ms
print(t('first_word_3(x)', setup='x = "asdfawe"*100000', number=10000, globals=globals())) # ~2005.8 msdef first_word_4(text):index = -1for pos, letter in enumerate(text):if letter == " ":index = posbreakreturn text[:index] if index != -1 else textprint(t('first_word_4(x)', setup='x = "asdf we"*10', number=10000, globals=globals())) # ~13.1 ms
print(t('first_word_4(x)', setup='x = "asdfawe"*10', number=10000, globals=globals())) # ~71.1 ms
print(t('first_word_4(x)', setup='x = "asdf we"*100000', number=10000, globals=globals())) # ~13.1 ms
print(t('first_word_4(x)', setup='x = "asdfawe"*100000', number=10000, globals=globals())) # ~788793.7 ms
############################################################################################################
So what conclusions can be made from all of this?1.Since every string is an instance of the string class, it's preferred to use its methods rather than implement
a new function which seems to be faster. It won't work faster in most of the cases. Compare first_word_2 and
first_word_4 for example.2.Despite the fact first_word_1 (which uses .split() method) looks nice and concise it works worse with long strings
than first_word_2 and first_word_3 do(they use .find() and .index() methods respectively). Especially in case there are
lots of spaces in the text.3.str.index() method works a bit faster than str.find() but only in case there is a space in the text. Otherwise it's
needed to handle an exception which takes some extra time. Thus, I'd use str.find() method in such kind of tasks.
"""
)
