Day - for 循环和索引

f, s = -1, 1t = 0while t<=13:    t= f + s    print(t,end= ' ')    f,s = s, t

0 1 1 2 3 5 8 13 21 

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 variable in iterable:

range(start, stop, step)

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 output0 1 2 3 4 5 6 7 8 9 second output1 2 3 4 5 6 7 8 9 third output5 6 7 8 9 fourth output1 3 5 7 9 fifth output3 6 9 12 sixth outputseventh output10 9 8 7 6 5 4 3 2 eighth output20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 nineth output20 18 16 14 12 10 8 6 4

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 outputa b c d e second outputa c e third outputi h g f e d c b fourth outputi h g f e d fifth outputsixth outputi g e seventh outputi h g f e d c b a ninth outputa b c d e f g h i tenth outputg h i eleventh outputc e g i

name = 'abcdefghi'print(name[0])print(name[-1])print(name[-2])print(name[-3])print(name[-1::-1])

aihgihgfedcba

name = input("enter word: ")if name[::] == name[::-1]:    print("palindrome")else:    print("not palindrome")

enter word: ammapalindromeenter word: ggfhyjdrnot 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) 

111112222333445

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 OutputA B C D E F G H I Second OutputX Y Z Third OutputZ Y X W V Fouth OutputA C E G I Fifth OutputI G E C A Sixth OutputZ X V T R P N L J H F D B