学习Python第二天,看了一天,有点头疼,准备先休息一会,再继续。有一点C语言和Java基础,学起来不是很费劲。学习热情尚好。
学习了dir,math模块,import加载模块,有跟Linux相似的地方。
>>> dir(math) ['__doc__', '__loader__', '__name__', '__package__', '__spec__', 'acos', 'acosh', 'asin', 'asinh', 'atan', 'atan2', 'atanh', 'ceil', 'copysign', 'cos', 'cosh', 'degrees', 'e', 'erf', 'erfc', 'exp', 'expm1', 'fabs', 'factorial', 'floor', 'fmod', 'frexp', 'fsum', 'gamma', 'gcd', 'hypot', 'inf', 'isclose', 'isfinite', 'isinf', 'isnan', 'ldexp', 'lgamma', 'log', 'log10', 'log1p', 'log2', 'modf', 'nan', 'pi', 'pow', 'radians', 'remainder', 'sin', 'sinh', 'sqrt', 'tan', 'tanh', 'tau', 'trunc'] >>> help(math.pow) Help on built-in function pow in module math:
pow(x, y, /) Return x**y (x to the power of y).
模块的加载方式:
>>> from __future__ import division >>> 5/2 2.5 >>> import math >>> help(math) Help on built-in module math:
NAME math
Python 3 中字符串的连接,3舍弃了``,反向单引号,因为辨识度差。print后面需要加括号().
>>> a=("free") >>> b=1988 >>> print a+'b' SyntaxError: Missing parentheses in call to 'print'. Did you mean print(a+'b')? >>> print a SyntaxError: Missing parentheses in call to 'print'. Did you mean print(a)? >>> print (a+b) Traceback (most recent call last): File "<pyshell#62>", line 1, in <module> print (a+b) TypeError: can only concatenate str (not "int") to str >>> print (a+'b') freeb >>> print (a+`b`) SyntaxError: invalid syntax >>> print (a+str'b') SyntaxError: invalid syntax >>> print (a+str(b)) free1988 >>>
转义符
"\"
赋值时,“r"表示为原始字符串。字符串里面的内容没有含义
>>> d="c:\news" >>> print (d) c: ews >>> d=r"c:\news" >>> print(d) c:\news >>> e="c:\\news" >>> print e SyntaxError: Missing parentheses in call to 'print'. Did you mean print(e)? >>> print (e) c:\news >>>
input函数,input()
>>> input("input your name:") input your name:python 'python' >>>
input结合print的小程序
print("Hello,World!") name=input("What's your name?") age=input("How old are you?") print("Your name is " + name) print("And you are "+age+" years old.") ten=int(age)+10 print("After ten years,you will be "+ str(ten) +" years old. ")
运行结果。
D:\WPy64-3720\ZZ>python 0515-2.py Hello,World! What's your name?Zoe How old are you?31 Your name is Zoe And you are 31 years old. After ten years,you will be 41 years old.
索引和切片
>>> lang=("study") >>> >>> lang[0] 's' >>> lang.index("d") 3 >>> a=lang[2:4] >>> a 'ud' >>> b=[2:] SyntaxError: invalid syntax >>> b=lang[2:] >>> b 'udy' >>>
序列的切片,一定要左边的数字小于右边的数字,lang[-1:-3]就没有遵守这个规则,返回的是一个空。
(前包括,后不包括)
如果第二个数字大于字符串的长度,得到的返回结果就自动到最大长度位置终止。