python_class 6.0001 lec2

最新推荐文章于 2023-08-14 10:02:59 发布

Dooz0

最新推荐文章于 2023-08-14 10:02:59 发布

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本文链接：https://blog.youkuaiyun.com/Dooz0/article/details/79334040

本文介绍了Python编程的基础知识，包括字符串操作、条件判断、循环结构等内容。通过实例演示了如何使用Python进行基本的数据处理和流程控制。

#-*- coding:utf-8 -*-
#!usr/env/bin python
""" 
lec2 branching, iteration 
strings
branching-if/elif/else
while loops
for   loops
"""

# strings
hi = "hello there"
name = "ana"
greet = hi + name
print(greet)
greeting = hi + " " + name
print(greeting)
silly = hi + (" " + name)*3
print(silly)
""" 字符串的运算，拼接，重复等 """

# output 
x = 1
print(x)
x_str = str(x)
print("my fav number is", x, ".", "x=", x)
print("my fav number is", x_str + "." + "x=" + x_str)
print("my fav number is" + x_str + "." + "x=" + x_str)
""" , 号默认是加空格的可用于整数 + 号用于字符串的拼接 """

# input
text = input("Type anything...")
print(5*text)
num = int(input("Type a number..."))
print(5*num)
""" 对于输入用input（）函数， 可以强制转换输入的类型（默认是字符类型）"""

# conditionals/branching
x = float(input("Enter a number for x: "))
y = float(input("Enter a number for y: "))
if x == y:
    print("x and y are equal")
    if y != 0:
        print("therefore, x/y is", x/y)
elif x < y:
    print("x is smaller")
elif x > y:
    print("y is smaller")
print("thanks!")
""" 
分支语句的用法，用于判断两个变量的关系, 跳转控制 
if ->elif ->else
C表示： if -> else if -> else
"""

# remainder 
num = int(input("Enter a number: "))
if num % 2 == 0:
    print("number is even")
else:
    print("number is odd")
""" 经常用于判断一个数的性质，素数，最大公约数等 """

# while loops
n = 0
while n < 5:
    print(n)
    n = n + 1
while n > 5 and n == 10:
    print("Just explain")
l = True
while l:
    print("control the while loop")
    n = int(input("Enter the n:"))
    if n == 11:
        l = False
""" while 循环可以控制一个循环一直执行， 但为了避免死循环需要
    设置一个出口推出循环。while + 逻辑语句控制-> 条件控制
"""

# for loops
for n in range(5):
    print(n)

mysum = 0
for i in range(10):
    mysum += 1
print(mysum)

mysum = 0
for i in range(7, 10):
    mysum += 1
print(mysum)

mysum = 0
for i in range(5, 11, 2):
    mysum += 1
    if mysum == 5:
        break
        mysum += 1
print(mysum)
""" for 循环可用于控制循环步数， 
    range(start, stop, step) 包含start但是不包含stop step控制步频
    for i in [1, 10] 控制i的取值
    for i in strings 可以取出字符串的每个字符
"""
# perfect squares
ans = 0
neg_flag = False
x = int(input("Enter an integer: "))
if x > 0:
    neg_flag = True
while ans**2 < x:
    ans = ans + 1
if ans**2 ==  x:
    print("Square root of", x, "is", ans)
else:
    print(x, "is not a perfect square")
    if neg_flag:
        print("Just checking... did you mean", -x, ">")
""" 理解程序的控制流 """