声明变量

>>> name = "Guido"

声明一个变量，变量名为：name 变量name的值为："Guido"

#可变的量

#存储数据

#避免重复代码

变量定义的规则

变量名只能是字母、数字或下划线的任意组合
变量名的第一个字符不能是数字
以下关键字不能声明为变量名：['and', 'as', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'exec', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'not', 'or', 'pass', 'print', 'raise', 'return', 'try', 'while', 'with', 'yield']
Age_of_guido #一般首字母大写，用于定义类；AGE_OF_GUIDO#大写，一般用于定义常量

变量的赋值

>>> name2 = name
>>> print(name,name2)
Guido Guido
>>> name = "Linus"
>>> print(name,name2)
Linus Guido

#%s %d %f %r

>>> msg = "my name is %s and age is %s" %("Guido",45)
>>> print(msg)
my name is Guido and age is 45

>>> msg = "my name is %s and age is %d" %("Guido",45)
>>> print(msg)
my name is Guido and age is 45

>>> msg = "my name is %s and age is %f" %("Guido",45)
>>> print(msg)
my name is Guido and age is 45.000000

二：数据类型

数字：

int（整型）、long(长整型)

float(浮点型)、complex(复数)

a = 27   数字

a = "27"  字符串

View Code

布尔&字符串：

布尔值 （真或假  Ture False 1或0）

字符串 

字符串常用功能：

移除空白、分割、长度、索引、切片、格式化输出

移除空白：

>>> name = "         Guido!"
>>> name
'         Guido!'
>>> name.strip()
'Guido!'

长度：

>>> len(name)
15

索引：

>>> name[9]
'G'
>>> name[10]
'u'
>>> name[11]
'i'
>>> name[12]
'd'

>>> name[13]
'o'

切片：

>>> name[9:13]
'Guid'
顾头不顾尾
>>> name[9:14]
'Guido'

字符串拼接：

>>> msg = "my name is " + name
>>> msg
'my name is Guido'

格式化输出：

>>> name = "Guido"
>>> age= 56
>>> msg = "my name is %s and i am %s years old!" % (name,age)
>>> msg
'my name is Guido and i am 56 years old!'

View Code

列表：

>>> names = ['linus','scott','guido']
>>> names[0]
'linus'
>>> names[1]
'scott'
>>> names[2]
'guido'

还可以反向取值

>>> names[-3]
'linus'

列表修改：

>>> names[-3] = "jack"
>>> names
['jack', 'scott', 'guido']

追加数据：

>>> names.append('tom')
>>> names
['jack', 'scott', 'guido', 'tom']

插入数据：

>>> names.insert(2,'larry')
>>> names
['jack', 'scott', 'larry', 'guido', 'tom']

删除数据：

>>> del names[2]
>>> names
['jack', 'scott', 'guido', 'tom']
>>> names.remove('tom')
>>> names
['jack', 'scott', 'guido']

修改数据：

>>> names
['jack', 'scott', 'guido', 'rain', 'rose']
>>> names.index('guido')
2
>>> names[2] = "elice"
>>> names
['jack', 'scott', 'elice', 'rain', 'rose']
>>> names[names.index('rain')] = 'RAIN'
>>> names
['jack', 'scott', 'elice', 'RAIN', 'rose']

统计数据：

['jack', 'scott', 'elice', 'RAIN', 'rose', 'scott', 'scott']
>>> names.count("scott")
3

>>> names.index("scott")
1

排序数据：

>>> names.sort()
>>> names
['RAIN', 'elice', 'jack', 'rose', 'scott', 'scott', 'scott']
>>> names.insert(2,"!")
>>> names.sort()
>>> names
['!', 'RAIN', 'elice', 'jack', 'rose', 'scott', 'scott', 'scott']

>>> names[2] = '5'
>>> names
['!', 'RAIN', '5', 'jack', 'rose', 'scott', 'scott', 'scott']
>>> names.sort()
>>> names
['!', '5', 'RAIN', 'jack', 'rose', 'scott', 'scott', 'scott']

>>> names.reverse()
>>> names
['scott', 'scott', 'scott', 'rose', 'jack', 'RAIN', '5', '!']

切片：

>>> names
['scott', 'scott', 'scott', 'rose', 'jack', 'RAIN', '5', '!']
>>> names[3:7]
['rose', 'jack', 'RAIN', '5']
>>> names[-1]
'!'
>>> names[-3:-1]
['RAIN', '5']
>>> names[-3:]
['RAIN', '5', '!']
>>> names[0:5]
['scott', 'scott', 'scott', 'rose', 'jack']
>>> names[:5]
['scott', 'scott', 'scott', 'rose', 'jack']

>>> names
['scott', 'scott', 'scott', 'rose', 'jack', 'RAIN', '5', '!']
>>> names[0:-1]
['scott', 'scott', 'scott', 'rose', 'jack', 'RAIN', '5']
>>> names[0:-1:1]    1代表步长
['scott', 'scott', 'scott', 'rose', 'jack', 'RAIN', '5']
>>> names[0:-1:2]    2代表步长
['scott', 'scott', 'jack', '5']

View Code

运算:

算数运算：
幂
>>> 5**2
25
除
>>> 5/3
1.6666666666666667
加
>>> 5+2
7
减
>>> 5-2
3
乘
>>> 5*2
10
取整除
>>> 5//2
2
取模-返回除法的余数，奇数偶数
>>> 5%2
1
>>> 5%3
2
>>> 5%4
1
>>> 5%5
0
比较运算：
>>> a = 10
>>> b = 5
>>> a == b
False
>>> a != b
True
>>> a > b
True
>>> a < b
False
>>> a >= b
True
>>> a <= b
False
赋值运算：
= 简单的赋值运算符 c = a + b将a + b的运算结果赋值为c
+= 加法赋值运算符  c += a等效于c = c + a
-=  减法赋值运算符  c -= a等效于c = c - a
+= 乘法赋值运算符  c *= a等效于c = c * a
+= 除法赋值运算符  c /= a等效于c = c / a
+= 取模赋值运算符  c %= a等效于c = c % a
+= 幂赋值运算符     c **= a等效于c = c ** a
+= 取整除赋值运算符  c //= a等效于c = c // a

逻辑运算  and、or、not
and
>>> today = "mon"
>>> tomorrow = "tes"
>>> today == "mon" and tomorrow == "teu"
False
>>> today == "mon" and tomorrow == "tes"
True

or
>>> today == "mon" or tomorrow == "tes"
True

not

成员运算：in、not in
>>> names
[1, 2, 3, 4, 5, 6]
>>> 7 in names
False
>>> 3 in names
True
>>> 10 not in names
True

身份运算：is、is not
>>> 8 is 8
True
>>> type(8)
<class 'int'>
>>> type(8) is int
True
>>> type(8) is not int
False
>>> type('eric') is not int
True

View Code

位运算：

#!/usr/bin/python

  
a = 60            # 60 = 0011 1100
b = 13            # 13 = 0000 1101
c = 0
  
c = a & b;        # 12 = 0000 1100
print "Line 1 - Value of c is ", c
  
c = a | b;        # 61 = 0011 1101
print "Line 2 - Value of c is ", c
  
c = a ^ b;        # 49 = 0011 0001 #相同为0，不同为1
print "Line 3 - Value of c is ", c
  
c = ~a;           # -61 = 1100 0011
print "Line 4 - Value of c is ", c
  
c = a << 2;       # 240 = 1111 0000
print "Line 5 - Value of c is ", c
  
c = a >> 2;       # 15 = 0000 1111
print "Line 6 - Value of c is ", c

三：表达式if ... else

用户登陆验证：python3

--python中单双引号没有任何区别

--用途：>>>msg = "my name's guido..." >>> msg = "a,'b',c,d"

#!/usr/bin/env python
name = input("用户名：")
pwd = input("密码：")

if name == "scott" and pwd =="tiger":
    print("Welcome,scott!")
else:
    print("用户名和密码错误！")

猜年龄：

#!/usr/bin/env python
my_age = 30
user_input = int(input("your guess num:"))
if user_input == my_age:
    print("Congratulations,you got it!")
elif user_input < my_age:
    print("think bigger!")
else:
    print("think smaller!")

四：表达式for loop

循环10次

for i in range(10):
    print("loop:",i)

输出：

loop: 0
loop: 1
loop: 2
loop: 3
loop: 4
loop: 5
loop: 6
loop: 7
loop: 8
loop: 9

需求一：还是上面的程序，但是遇到小于5的循环次数就不走了，直接跳入下一次循环　

for i in range(10):
    if i<5:
        continue #不往下进行，直接进入下一次loop
    print("loop:",i)

View Code

需求二：还是上面的程序，但是遇到大于5的循环次数就不走了，直接退出

for i in range(10):
    if i>5:
        break #不往下进行，直接跳出整个loop
    print("loop:",i)

View Code

猜年龄

AGE = 56
for i in range(10):
    if i == 3:
        print("too many attemps,bye...")
        break
    guess_num = int(input("your guess num:"))
    if guess_num == AGE:
        print("Congratulations,you got it.")
        break
    elif guess_num > AGE:
        print("try smaller...")
    else:
        print("try bigger...")

For 循环：引入计数器的场景。 break：跳出整个循环

AGE = 56
count = 0
for i in range(10):
    if count == 3:
        user_confirm = input("do you want to keep guessing.?").strip()
        if user_confirm == "y":
            count = 0
        else:
            break
    guess_num = int(input("your guess num:"))
    if guess_num == AGE:
        print("Congratulations,you got it.")
        break
    elif guess_num > AGE:
        print("try smaller...")
    else:
        print("try bigger...")

    count += 1

For循环（break，continue）

continue:跳出本次循环，进入下一次循环

for i in range(10):
    if i == 5:
        continue
    print("loop:",i)

示例1

for i in range(10):
    if i == 5:
        for j in range(10):
            print("inner loop",j)
        continue
    print("loop",i)

示例2

for i in range(10):
    if i == 5:
        for j in range(10):
            print("inner loop",j)
            if j == 6:
                break
        continue
    print("loop",i)

示例3

五：while loop

死循环：

count = 0
while True:
    print("count:",count)
    count +=1

计数器：

count = 0
while True:
    if count < 3:

        user = input("请输入您的姓名： ")
        pwd = input("请输入账户密码： ")

        if user == "elon"  and pwd == "elon":
            print("Congratulations!!!")
            break
        else:
            count +=1
    else:
        print("too many error,bye!")

        break

计数器

循环100次就退出

count = 0
while True:
    print("count:",count)
    count +=1
    if count == 100:
        print("over!")
        break

View Code

for 循环的，如何实现让用户不断的猜年龄，但只给最多3次机会，再猜不对就退出程序。

my_age = 30
count = 0
while count < 3:
    user_input = int(input("your guess num:"))
    if user_input == my_age:
        print("Congratulations,you got it!")
        break
    elif user_input < my_age:
        print("think bigger!")
    else:
        print("think smaller!")
    count += 1
else:
    print("超过最大输入次数！")

View Code

import time
t0_start = time.time()
count0 = 0
while True:
    if count0 == 1000000:
        break
    count0 += 1
print("cost0:",time.time()-t0_start,count0)
t_start = time.time()
count = 0
while count < 1000000:
    count += 1
print("cost:",time.time()-t_start,count)

View Code

day01-Python基础 一：变量 二：数据类型 四：表达式for loop 五：while loop

二：数据类型

四：表达式for loop

五：while loop

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day01-Python基础一：变量二：数据类型四：表达式for loop 五：while loop