python基础知识4

函数的使用示例

• abs(x)

>>> abs(10)
10
>>> abs(0)
0
>>> abs(-10)
10
>>> abs(1+2j)
2.23606797749979
>>> pow(5,0.5)
2.23606797749979

• divmod(x,y)

>>> divmod(10,3)
(3, 1)
>>> divmod(25,2)
(12, 1)
>>> 

• pow(x,y)

>>> pow(2,5)
32
>>> pow(25,0.5)
5.0
>>> pow(100,0)
1

• round(x,d)

>>> round(10/3,3)
3.333
>>> round(2/3,3)
0.667
>>> 

• z.real和z.imag（x）

>>> z=1+2j
>>> z.real
1.0
>>> z.imag
2.0
>>> 

• min/max(x1,x2….)

>>> max(1,2,5,545,54631,5646531,56)
5646531
>>> min(1,2,5,3,5,2,-545,-1)
-545
>>> 

• int/float/complex()
  int和float无法将complex转换为int/float

>>> int(232.214551354)
232
>>> float(1+8j)
Traceback (most recent call last):
  File "<pyshell#20>", line 1, in <module>
    float(1+8j)
TypeError: can't convert complex to float
>>> int(1+2j)
Traceback (most recent call last):
  File "<pyshell#21>", line 1, in <module>
    int(1+2j)
TypeError: can't convert complex to int
>>> float(12.65)
12.65
>>> float(12)
12.0
>>> complex(12)
(12+0j)
>>> complex(12.65)
(12.65+0j)
>>> 

• eval（）

>>> s='123'
>>> eval(s)
123
>>> 

实例一：温度转换

#TempConvert.py //注释行
TempStr = input("请输入带有符号的温度值: ")
if TempStr[-1] in ['F', 'f']:  
    C = (eval(TempStr[0:-1]) - 32)/1.8
    print("转换后的温度是{:.2f}C".format(C)) 
elif TempStr[-1] in ['C', 'c']:
    F = 1.8*eval(TempStr[0:-1]) + 32
    print("转换后的温度是{:.2f}F".format(F))
else:
    print("输入格式错误")

实例二：蟒蛇

#PythonDraw.py                                               注释
import turtle
turtle.setup(650, 350, 200, 200)                设置画布的长宽以及在屏幕上的位置
turtle.penup()                                     提起画笔，准备绘画
turtle.fd(-250)                                  向前移动-250像素长度，即后退250
turtle.pendown()                                    画笔落下
turtle.pensize(25)                              画笔宽度的设置
turtle.pencolor("purple")                       画笔颜色的设置
turtle.seth(-40)                                    画笔角度的设置为绝对-40°
for i in range(4):                              
    turtle.circle(40, 80)                         画笔左边画80°的圆，半径为40
    turtle.circle(-40, 80)                          画笔左边画80°的圆，半径为40
turtle.circle(40, 80/2)                             画笔左边画40°的圆，半径为40
turtle.fd(40)
turtle.circle(16, 180)
turtle.fd(40 * 2/3)
turtle.done()                                                                                     

实例三：玫瑰花（请读者自行参照上一章内容分析）

import turtle

# 设置初始位置

turtle.penup()

turtle.left(90)

turtle.fd(200)

turtle.pendown()

turtle.right(90)

# 花蕊

turtle.fillcolor("red")

turtle.begin_fill()

turtle.circle(10,180)

turtle.circle(25,110)

turtle.left(50)

turtle.circle(60,45)

turtle.circle(20,170)

turtle.right(24)

turtle.fd(30)

turtle.left(10)

turtle.circle(30,110)

turtle.fd(20)

turtle.left(40)

turtle.circle(90,70)

turtle.circle(30,150)

turtle.right(30)

turtle.fd(15)

turtle.circle(80,90)

turtle.left(15)

turtle.fd(45)

turtle.right(165)

turtle.fd(20)

turtle.left(155)

turtle.circle(150,80)

turtle.left(50)

turtle.circle(150,90)

turtle.end_fill()



# 花瓣1

turtle.left(150)

turtle.circle(-90,70)

turtle.left(20)

turtle.circle(75,105)

turtle.setheading(60)

turtle.circle(80,98)

turtle.circle(-90,40)



# 花瓣2

turtle.left(180)

turtle.circle(90,40)

turtle.circle(-80,98)

turtle.setheading(-83)



# 叶子1

turtle.fd(30)

turtle.left(90)

turtle.fd(25)

turtle.left(45)

turtle.fillcolor("green")

turtle.begin_fill()

turtle.circle(-80,90)

turtle.right(90)

turtle.circle(-80,90)

turtle.end_fill()



turtle.right(135)

turtle.fd(60)

turtle.left(180)

turtle.fd(85)

turtle.left(90)

turtle.fd(80)



# 叶子2

turtle.right(90)

turtle.right(45)

turtle.fillcolor("green")

turtle.begin_fill()

turtle.circle(80,90)

turtle.left(90)

turtle.circle(80,90)

turtle.end_fill()



turtle.left(135)

turtle.fd(60)

turtle.left(180)

turtle.fd(60)

turtle.right(90)

turtle.circle(200,60)
turtle.seth(60)
turtle.fd(100)
turtle.seth(-60)
turtle.fd(100)
turtle.seth(60)
turtle.fd(100)
turtle.seth(-60)
turtle.fd(100)
turtle.seth(60)
turtle.fd(50)
turtle.seth(0)
turtle.fd(50)
turtle.left(120)
turtle.fd(50)
turtle.seth(-120)
turtle.fd(50)
turtle.seth(0)
turtle.fd(50)
turtle.seth(-60)
turtle.fd(50)


turtle.done()
turtle.stamp()

字符串函数使用简例：

>>> 'HELLO,WRITER'.lower()
'hello,writer'
>>> 'hello,world'.upper()
'HELLO,WORLD'
>>> 'hello'.isupper()
False
>>> 'hello,world'.islower()
True
>>> 
>>> 'hello,i love you!'.isalpha()
False
>>> 'i love you'.isalpha()
False
>>> 'hello'.isalpha()
True
>>> '  \n '.isspace()
True
>>> 'hello world'.startswith('hello')
True
>>> 'hello,world'.endswith('world')
True
>>> 'hello,world'.endswith('ld')
True
>>> ','.join(['cats','rats','bats'])
'cats,rats,bats'
>>> '-'.join(['h','e','l','l','o'])
'h-e-l-l-o'
>>> spam='''hello world
ni hao
nice to meet you
'''
>>> spam.split('\n')
['hello world', 'ni hao', 'nice to meet you', '']
>>> 'eeeeeeeeeeeeeeeeeeeeee'.count('e')
22
>>> 'hello world'.rjust(20,'=')
'=========hello world'
>>> 'hello world'.ljust(20,'=')
'hello world========='
>>> 'hello world'.center(20,'=')
'====hello world====='
>>> '  hello world '.lstrip(' ')
'hello world '
>>> 'hello world'.strip(' ')
'hello world'

time库

• time.time()

>>> import time
>>> time.time()
1534498794.9012585
>>> 

• time.ctime()

>>> time.ctime()
'Fri Aug 17 17:41:21 2018'

• time.gmtime()

>>> time.gmtime()
time.struct_time(tm_year=2018, tm_mon=8, tm_mday=17, tm_hour=9, tm_min=41, tm_sec=28, tm_wday=4, tm_yday=229, tm_isdst=0)

• time.sleep()

>>> for i in range(5):                      以渐变的形式打印出来
    print(i)
    time.sleep(i)


0
1
2
3
4

• datetime.datetime.now()

>>> import datetime
>>> datetime.datetime.now()
datetime.datetime(2018, 8, 17, 17, 45, 43, 508754)

• datetime.datetime()

>>> datetime.datetime(2018,7,7,7,7,7)
datetime.datetime(2018, 7, 7, 7, 7, 7)

• datetime.datetime.fromtimestamp()

>>> datetime.datetime.fromtimestamp(time.time())
datetime.datetime(2018, 8, 17, 17, 53, 35, 903952)
>>> datetime.datetime.fromtimestamp(10000000)
datetime.datetime(1970, 4, 27, 1, 46, 40)

timedelta数据类型

>>> delta=datetime.timedelta(days=11,hours=12,minutes=15,seconds=11)
>>> delta.days
11
>>> delta.seconds
44111
>>> delta.total_seconds()
994511.0
>>> str(delta)
'11 days, 12:15:11'
>>> 

• strftime()

>>> q=datetime.datetime(2015,10,10,10,10,10)
>>> q.strftime('%Y/%m/%d %H:%M:%S')
'2015/10/10 10:10:10'
>>> q.strftime('%I:%M %p')
'10:10 AM'
>>> q.strftime('%B OF %y')
'October OF 15'
>>> 

• strptime()

>>> datetime.datetime.strptime('2015/11/11 16:29:21','%Y/%m/%d %H:%M:%S')
datetime.datetime(2015, 11, 11, 16, 29, 21)

实例四：文本进度条

#TextProBarV3.py
import time
scale = 50
print("执行开始".center(scale//2, "-"))
start = time.perf_counter()    调用时间函数记录初始时间
for i in range(scale+1):
    a = '*' * i
    b = '.' * (scale - i)
    c = (i/scale)*100
    dur = time.perf_counter() - start
    print("\r{:^3.0f}%[{}->{}]{:.2f}s".format(c,a,b,dur),end='')
    time.sleep(0.1)
print("\n"+"执行结束".center(scale//2,'-'))

• 列表内容

实例五：天天向上

day=input()
day=eval(day)
q=w=1
for i in range(365):

        q=q*(1+day*0.001)
for j in range(365):
    w=w*(1-day*0.001)
s=q//w
print('{:.2f}'.format(q),'{:.2f}'.format(w),'{:.0f}'.format(s),sep=',')

实例六：凯撒密码

temp=input()
a=len(temp)
b=''
for i in range(a):
    c=ord(temp[i])       
    if c==32:           空格值为32
        b+=' '
    else :a
        d=(c-97+3)%26
        r=chr(d+97)          97为a的unicode值
        b+=r
print(b)

• ord（）函数取得每一个字符串的unicode值
• 将每一个字母的unicode—97+3并取余数得到原有字符的+3后的字符
• 最后将Unicode值+97转换为字符值