本文是笔者在学习MOOC课程《Python语言基础与应用》 (北京大学-陈斌)中根据上机课时的要求写下在代码
课程总链接:
本节课链接
数值基本运算: 33和7
+, -, *, /, //, %, **
hex(), oct(), bin()
1 Python 3.7.0 (default, Jun 28 2018, 08:04:48) [MSC v.1912 64 bit (AMD64)] :: Anaconda, Inc. on win32 2 Type "help", "copyright", "credits" or "license" for more information. 3 >>> 33+7 4 40 5 >>> 33-7 6 26 7 >>> 33*7 8 231 9 >>> 33/7 10 4.714285714285714 11 >>> 33//7 12 4 13 >>> 33%7 14 5 15 >>> 33**7 16 42618442977 17 >>> 7**33 18 7730993719707444524137094407 19 >>> 33**33 20 129110040087761027839616029934664535539337183380513 21 >>> hex(33) 22 ‘0x21‘ 23 >>> hex(7) 24 ‘0x7‘ 25 >>> oct(7) 26 ‘0o7‘ 27 >>> oct(33) 28 ‘0o41‘ 29 >>> bin(33) 30 ‘0b100001‘ 31 >>> bin(7) 32 ‘0b111‘
类型转换
1, 0, ‘abc‘, None, 1.2, False, ‘‘
str(), bool(), int(), float()
is None, ==, !=
1 >>> str(1) 2 ‘1‘ 3 >>> str(0) 4 ‘0‘ 5 >>> bool(1) 6 True 7 >>> bool(0) 8 False 9 >>> bool(‘abc‘) 10 True 11 >>> int(‘abc‘) 12 Traceback (most recent call last): 13 File "<stdin>", line 1, in <module> 14 ValueError: invalid literal for int() with base 10: ‘abc‘ 15 >>> int(‘a‘) 16 Traceback (most recent call last): 17 File "<stdin>", line 1, in <module> 18 ValueError: invalid literal for int() with base 10: ‘a‘ 19 >>> float(‘abc‘) 20 Traceback (most recent call last): 21 File "<stdin>", line 1, in <module> 22 ValueError: could not convert string to float: ‘abc‘ 23 >>> float(1) 24 1.0 25 >>> str(None) 26 ‘None‘ 27 >>> int(None) 28 Traceback (most recent call last): 29 File "<stdin>", line 1, in <module> 30 TypeError: int() argument must be a string, a bytes-like object or a number, not ‘NoneType‘ 31 >>> int(‘None‘) 32 Traceback (most recent call last): 33 File "<stdin>", line 1, in <module> 34 ValueError: invalid literal for int() with base 10: ‘None‘ 35 >>> int(1.2) 36 1 37 >>> int(False) 38 0 39 >>> int(True) 40 1 41 >>> float(‘‘) 42 Traceback (most recent call last): 43 File "<stdin>", line 1, in <module> 44 ValueError: could not convert string to float: 45 >>> bool(‘‘) 46 False 47 >>> 1 is None 48 False 49 >>> 0 is None 50 False 51 >>> ‘‘ is None 52 False 53 >>> 1==1.2 54 False 55 >>> False is None 56 False 57 >>> True is None 58 False
字符串基本操作
+, *, len(), [], in
ord(), chr()
含有中文的字符串
1 >>> a=‘Congratulations‘ 2 >>> b=‘misunderstandings‘ 3 >>> a+b 4 ‘Congratulationsmisunderstandings‘ 5 >>> a+‘ ‘+b 6 ‘Congratulations misunderstandings‘ 7 >>> len(a) 8 15 9 >>> len(b) 10 17 11 >>> c in a 12 Traceback (most recent call last): 13 File "<stdin>", line 1, in <module> 14 NameError: name ‘c‘ is not defined 15 >>> ‘c‘ in a 16 False 17 >>> ‘s‘ in b 18 True 19 >>> ‘C‘ in a 20 True 21 >>> [a] 22 [‘Congratulations‘] 23 >>> ord(‘a‘) 24 97 25 >>> chr(86) 26 ‘V‘ 27 >>> ord(a) 28 Traceback (most recent call last): 29 File "<stdin>", line 1, in <module> 30 TypeError: ord() expected a character, but string of length 15 found 31 >>> c=‘你好‘ 32 >>> d=‘国‘ 33 >>> len(c) 34 2 35 >>> len(d) 36 1 37 >>> ord(d) 38 22269 39 >>> chr(83475) 40 ‘??‘ 41 >>> chr(22270) 42 ‘图‘ 43 >>> chr(24343) 44 ‘弗‘
字符串高级操作
s=‘abcdefg12345‘
切片:获得defg12,获得fg12345,获得54321,
获得aceg2
>>> s=‘abcdefg12345‘ >>> s1=s[3:9] >>> s1 ‘defg12‘ >>> s2=s[5:] >>> s2 ‘fg12345‘ >>> s3=s[-1:-6] >>> s3 ‘‘ >>> s3=s[-1:-6:1] >>> s3 ‘‘ >>> s ‘abcdefg12345‘ >>> s3=s[-1:] >>> s3 ‘5‘ >>> s4=s[0:9:2] >>> s4 ‘aceg2‘ >>> s3=s[::-1] >>> s3 ‘54321gfedcba‘ >>> s3=s[-1:-6] >>> s3 ‘‘ >>> s3=s[-1:-6:] >>> s3 ‘‘ >>> s3=s[-5] >>> s3 ‘1‘ >>> s3=s[-5::] >>> s3 ‘12345‘ >>> s3=s[-6:-1:-1] >>> s3 ‘‘ >>> s3.index(5) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: must be str, not int >>> s3.index(‘5‘) Traceback (most recent call last): File "<stdin>", line 1, in <module> ValueError: substring not found >>> s.index(‘5‘) 11 >>> s.index(‘1‘) 7 >>> s3=s[11:7:-1] >>> s3 ‘5432‘ >>> s3=s[11:8:-1] >>> s3 ‘543‘ >>> s3=s[11:6:-1] >>> s3 ‘54321‘ >>> >>> s3=s[-1:-6:-1] >>> s3 ‘54321‘ >>> s3=s[-1:6:-1] >>> s3 ‘54321‘
通常一个切片操作要提供三个参数 [start_index: stop_index: step]
start_index是切片的起始位置
stop_index是切片的结束位置(不包括)
step可以不提供,默认值是1,步长值不能为0,不然会报错ValueError。
当 step 是正数时,以list[start_index]元素位置开始, step做为步长到list[stop_index]元素位置(不包括)为止,从左向右截取,
start_index和stop_index不论是正数还是负数索引还是混用都可以,但是要保证 list[stop_index]元素的【逻辑】位置
必须在list[start_index]元素的【逻辑】位置右边,否则取不出元素。
比如下面的几个例子都是合法的:
>>> alist = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> alist[1:5]
[1, 2, 3, 4]
>>> alist[1:-1]
[1, 2, 3, 4, 5, 6, 7, 8]
>>> alist[-8:6]
[2, 3, 4, 5]
当 step 是负数时,以list[start_index]元素位置开始, step做为步长到list[stop_index]元素位置(不包括)为止,从右向左截取,
start_index和stop_index不论是正数还是负数索引还是混用都可以,但是要保证 list[stop_index]元素的【逻辑】位置
必须在list[start_index]元素的【逻辑】位置左边,否则取不出元素。详见链接。
t=‘Mike and Tom‘
split拆分
upper/lower/swapcase修改大小写
ljust/center/rjust排版30位宽度左中右对齐
replace将Mike替换为Jerry
1 >>> t=‘Mike and Tom‘ 2 >>> list1=t.split(‘ ‘) 3 >>> list1 4 [‘Mike‘, ‘and‘, ‘Tom‘] 5 >>> tuple1=tuple(list1) 6 >>> tuple1 7 (‘Mike‘, ‘and‘, ‘Tom‘) 8 >>> t.upper() 9 ‘MIKE AND TOM‘ 10 >>> t.lower() 11 ‘mike and tom‘ 12 >>> t.swapcase() 13 ‘mIKE AND tOM‘ 14 >>> t.ljust() 15 Traceback (most recent call last): 16 File "<stdin>", line 1, in <module> 17 TypeError: ljust() takes at least 1 argument (0 given) 18 >>> t.ljust(1) 19 ‘Mike and Tom‘ 20 >>> t.ljust(3) 21 ‘Mike and Tom‘ 22 >>> t.ljust(50,‘*‘) 23 ‘Mike and Tom**************************************‘ 24 >>> t.rjust(50,‘*‘) 25 ‘**************************************Mike and Tom‘ 26 >>> t.center(30,‘*‘) 27 ‘*********Mike and Tom*********‘ 28 >>> t.replace(‘Mike‘,‘Jerry‘) 29 ‘Jerry and Tom‘ 30 >>> t 31 ‘Mike and Tom‘
swapcase() 方法用于对字符串的大小写字母进行转换。
Python ljust() 方法返回一个原字符串左对齐,并使用空格填充至指定长度的新字符串。如果指定的长度小于原字符串的长度则返回原字符串。
语法
ljust()方法语法:
str.ljust(width[, fillchar])
参数
width -- 指定字符串长度。
fillchar -- 填充字符,默认为空格。
返回值
返回一个原字符串左对齐,并使用空格填充至指定长度的新字符串。如果指定的长度小于原字符串的长度则返回原字符串。
实例
以下实例展示了ljust()的使用方法:
str = "this is string example....wow!!!";
print str.ljust(50, ‘0‘);
以上实例输出结果如下:
this is string example....wow!!!000000000000000000
原文地址:https://www.cnblogs.com/flyingtester/p/12360805.html