标签:index return name Python move 基础 print def
1. if the string contains both ' and " can be identifified by the escape character
print("I\'m \"OK\"")
2. None can't be understood as 0, because 0 is meaningful, and none is a special null value
3. A chinese character usually occupies 3 bytes after UTF-8 encoding, while an English character only occupies 1 byte.
print(len("中文".encode("utf-8")))
4. new features in python3.8
name = 'miku'
age = 16
print(f"{name}\'s age is {age}")
5. # type of tuple
a = ()
b = (3,)
c = (3, 4, 5)
6. for -> new features
L = ['Bart', 'Lisa', 'Adam']
for name in L:
print(f"Hello, {name}")
7. Parameter check
def my_abs(x):
if not isinstance(x, (int, float)):
raise TypeError('bad operand type')
if x >= 0:
return x
else:
return -x
8. Solving equations
import math
def quadratic(a, b, c):
if b * b - 4 * a * c < 0:
print("测试失败")
else:
return (-1 * b + math.sqrt(b*b - 4 * a * c)) / (2 * a), (-1 * b - math.sqrt(b*b - 4 * a * c)) / (2 * a)
print(quadratic(1, 4 ,0))
9. One thing to keep in mind when defining default parameters: Default parameters must point to immutable objects!
10. Variable parameters, keywords parameters
def calc(*numbers):
sum = 0
for n in numbers:
sum = sum + n * n
return sum
nums = [1, 2, 3]
print(calc(1, 2))
print(calc())
print(calc(*nums))
def person(name, age, **kw):
print('name:', name, 'age:', age, 'other:', kw)
person('Adam', 45, gender='M', job='Engineer')
*args是可变参数,args接收的是一个tuple; **kw是关键字参数,kw接收的是一个dict。 定义命名的关键字参数在没有可变参数的情况下不要忘了写分隔符*,否则定义的将是位置参数。
11. 请编写move(n, a, b, c)函数,它接收参数n,表示3个柱子A、B、C中第1个柱子A的盘子数量,然后打印出把所有盘子从A借助B移动到C的方法
# 利用递归函数移动汉诺塔:
def move(n, a, b, c):
if n == 1:
print('move', a, '-->', c)
else:
move(n-1, a, c, b)
move(1, a, b, c)
move(n-1, b, a, c)
move(4, 'A', 'B', 'C')
12. 利用切片操作,实现一个trim()函数,去除字符串首尾的空格,注意不要调用str的strip()方法
def trim(s):
index_1 = -1
index_2 = 0
flag_1 = False
flag_2 = False
for i in range(len(s)):
if s[i].isalpha():
flag_1 = True
if s[len(s) - 1 - i].isalpha():
flag_2 = True
# 解决前面的空格
if s[i] == " " and not flag_1:
index_1 = i
print(index_1)
# 解决后面的空格
if s[len(s) -1 - i] == " " and not flag_2:
index_2 -= 1
print(index_2)
if index_2 == 0:
return s[index_1 + 1 :]
else:
return s[index_1 + 1 : index_2]
print(trim(" hello World"))
13. how to judge an object is an iterable object ? The method is to determine the Iterable type of the collections module
from collections.abc import Iterable
import collections
isinstance('abc', Iterable) # str是否可迭代
isinstance(123, Iterable) # 整数是否可迭代
凡是可作用于for循环的对象都是Iterable类型; 凡是可作用于next()函数的对象都是Iterator类型,它们表示一个惰性计算的序列; 集合数据类型如list、dict、str等是Iterable但不是Iterator,不过可以通过iter()函数获得一个Iterator对象。 Python的for循环本质上就是通过不断调用next()函数实现的
L1 = ['Hello', 'World', 18, 'Apple', None]
L2 = [s.lower() if isinstance(s, str) else s for s in L1]
print(L2)
# Incoming function
def add(x, y, f):
return f(x) + f(y)
print(add(-5, 6, abs))
标签:index,return,name,Python,move,基础,print,def 来源: https://www.cnblogs.com/xmdykf/p/13489883.html
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