查找斐波那契数列：
生成达到给定数字的斐波那契数列。
示例：输入：10 → 输出：0, 1, 1, 2, 3, 5, 8.
f, s = -1, 1 t = 0 while t<=13: t= f + s print(t,end= ' ') f,s = s, t
0 1 1 2 3 5 8 13 21
不使用第三个变量查找斐波那契数列：
f, s = -1, 1 while f+s<=13: print(f + s,end= ' ') f,s = s, f + s
0 1 1 2 3 5 8 13
for 循环是编程中使用的控制流语句，用于将代码块重复特定次数或迭代序列。
语法：
for variable in iterable:
步骤运算符：
步骤运算符是指为循环中的迭代指定增量（或步骤）的能力。在 python 中，这通常与 range() 函数一起使用，它允许指定一个步骤来控制循环变量在每次迭代后如何变化。
语法：
range(start, stop, step)
start：序列的起始值（含）。
stop：序列的停止值（不包括）。
步骤：序列在每次迭代中增加（或减少，如果为负）的量。
print("first output") for no in range(10): print(no, end=' ') print(" second output") for no in range(1,10): print(no, end=' ') print(" third output") for no in range(5,10): print(no, end=' ') print(" fourth output") for no in range(1,10,2): print(no, end=' ') print(" fifth output") for no in range(3,15,3): print(no, end=' ') print(" sixth output") for no in range(10,1): print(no, end=' ') print(" seventh output") for no in range(10,1,-1): print(no, end=' ') print(" eighth output") for no in range(20,3,-1): print(no, end=' ') print(" nineth output") for no in range(20,2,-2): print(no, end=' ')
first output 0 1 2 3 4 5 6 7 8 9 second output 1 2 3 4 5 6 7 8 9 third output 5 6 7 8 9 fourth output 1 3 5 7 9 fifth output 3 6 9 12 sixth output seventh output 10 9 8 7 6 5 4 3 2 eighth output 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 nineth output 20 18 16 14 12 10 8 6 4
索引：
索引是指使用元素的位置或索引来访问序列（如列表、元组或字符串）中的元素。
索引类型：
1.正索引：
第一个元素从 0 开始。
2.负索引：
最后一个元素从 -1 开始。
name = 'abcdefghi' print("first output") for letter in name[0:5]: print(letter, end=' ') print(" second output") for letter in name[0:6:2]: print(letter, end=' ') print(" third output") for letter in name[8:0:-1]: print(letter, end=' ') print(" fourth output") for letter in name[8:2:-1]: print(letter, end=' ') print(" fifth output") for letter in name[8:-1:-1]: print(letter, end=' ') print(" sixth output") for letter in name[8:3:-2]: print(letter, end=' ') print(" seventh output") for letter in name[8::-1]: print(letter, end=' ') print(" ninth output") for letter in name[::]: print(letter, end=' ') print(" tenth output") for letter in name[6::]: print(letter, end=' ') print(" eleventh output") for letter in name[2::2]: print(letter, end=' ')
first output a b c d e second output a c e third output i h g f e d c b fourth output i h g f e d fifth output sixth output i g e seventh output i h g f e d c b a ninth output a b c d e f g h i tenth output g h i eleventh output c e g i
name = 'abcdefghi' print(name[0]) print(name[-1]) print(name[-2]) print(name[-3]) print(name[-1::-1])
a i h g ihgfedcba
编写一个程序来检查给定的字符串是否是回文
name = input("enter word: ") if name[::] == name[::-1]: print("palindrome") else: print("not palindrome")
enter word: amma palindrome enter word: ggfhyjdr not palindrome
name = 'abcd' print(name * 3)
abcdabcdabcd
name = 'abcd' print(name + 3)
typeerror: can only concatenate str (not "int") to str
this error occurs because you're trying to concatenate a string (name) with an integer (3) using the + operator. in python, the + operator for strings is used for concatenation, but both operands must be strings.
for num in range(5): print("* " * num)
* * * * * * * * * *
for num in range(1,6): print("* " * num)
* * * * * * * * * * * * * * *
for num in range(5,0,-1): print("* " * num)
* * * * * * * * * * * * * * *
digit = "1" for num in range(5,0,-1): print(digit * num) digit = str(int(digit)+1)
11111 2222 333 44 5
任务：
abcdefghi
xyz
zyxwv
acegi
伊格卡
zxvtrpnljhfdb
word = 'abcdefghijklmnopqrstuvwxyz' print("first output") for letter in word[0:9]: print(letter , end=" ") print(" second output") for letter in word[23::]: print(letter , end=" ") print(" third output") for letter in word[-1:-6:-1]: print(letter , end=" ") print(" fouth output") for letter in word[0:9:2]: print(letter , end=" ") print(" fifth output") for letter in word[8::-2]: print(letter , end=" ") print(" sixth output") for letter in word[-1::-2]: print(letter , end=" ")
First Output A B C D E F G H I Second Output X Y Z Third Output Z Y X W V Fouth Output A C E G I Fifth Output I G E C A Sixth Output Z X V T R P N L J H F D B
