Python 入门日记(二)—— 变量与简单数据类型
2020.07.05 Python 入门的 Day2
成就:部分字符串、整数、浮点数操作
字符串:
- 字符串就是一系列字符。在 Python 中,用括号括起来的都是字符串,其中的引号可以是单引号,也可以是双引号。
- 方法是 Python 可对数据执行的操作。每个方法后面都跟着一对括号,用以提供必要的信息。
- 通过方法对字符串的改动是暂时的,方法结束后,字符串就会恢复。永久保存改动的方式就是通过赋值记录下来。
name = "Everything has changed!" print(name) # .title() 是一个使字符串中的每个单词首字母大写、其余字母小写的方法 print(name.title()) # 使方法的结果得以保存的方法就是赋值 name = name.title() print(name)
- title() 的作用是使字符串中所有单词的首字母都大写、除了首字母以外的其他字母都小写的方法。
- upper() 的作用是使字符串中所有单词的字母都大写。
- lower() 的作用是使字符串中所有单词的字母都小写。
- replace() 的作用是将字符串中的特定的单词全部替换为另一个单词。
name = "Everything hAs cHAnged aGain!" print(name.title()) print(name.upper()) print(name.lower()) name.replace('aGain', 'again and again')
- Python 用加号(+)来合并字符串,这种合并字符串的方法称为拼接。
- 在编程中,空白泛指任何非打印字符,如空格、制表符合换行符。字符组合 \t 可用于添加制表符,\n 用于添加换行符。
- 输出字符组合 \t 或 \n 需要用 \\t 或 \\n。
- rstrip() 是删除字符串末尾空白的方法,lstrip() 是删除字符串开头空白的方法,strip() 是删除字符串两端空白的方法。
name = ' Everything has changed again and again! ' thought = "I think." print(name.rstrip()) print(name.lstrip()) print(name.strip()) # 删除字符串末尾、开头、两端的空白 name = name.strip() + "," + " " + thought print(name) # 字符串拼接 print("\t" + name) print("\n\t" + name) print("\\t") print("\\n") print("\\t\\n") print("\t\\t")
- 在单引号(')括起来的字符串中使用(')会导致错误。
数字:
- 整数支持加(+)、减(-)、乘(*)、除(/)运算。
- Python 将带小数点的数字都成为浮点数。
- Python 使用两个乘号表示乘方运算。
- 函数 str() 将非字符串值表示为字符串。
print(1 + 7) print(19 - 11) print(2 * 4) print(16 / 2) print(2 ** 3) print(2 ** 0.5) age = 20 message = "Happy " + str(age) + "th Birthday!" print(message) # Twenty is also a good thing!
Python 之禅:
import this
- The Zen of Python, by Tim Peters
- Beautiful is better than ugly.
- Explicit is better than implicit.
- Simple is better than complex.
- Complex is better than complicated.
- Flat is better than nested.
- Sparse is better than dense.
- Readability counts.
- Special cases aren't special enough to break the rules.
- Although practicality beats purity.
- Errors should never pass silently.
- Unless explicitly silenced.
- In the face of ambiguity, refuse the temptation to guess.
- There should be one-- and preferably only one --obvious way to do it.
- Although that way may not be obvious at first unless you're Dutch.
- Now is better than never.
- Although never is often better than *right* now.
- If the implementation is hard to explain, it's a bad idea.
- If the implementation is easy to explain, it may be a good idea.
- Namespaces are one honking great idea -- let's do more of those!