Python语法入门-课件下载

链接: https://pan.baidu.com/s/1h1RuWimLicVanK8xCka_xA 提取码: x264

if条件判断

condition为布尔值、布尔运算、成员运算符

通常我们理解的condition为布尔值

#Tab
condition = True

if condition:
    print('condition为True')
else:
    print('condition为False')

condition为True

age = 17

if age>=18:
    print('你是成年人了')
else:
    print('你还是个孩子')

你还是个孩子

age = 20

if age>=55:
    print('老年人')
elif 35<=age<55:
    print('中年')
elif 18<=age<35:
    print('青年')
elif 0<=age<18:
    print('儿童')

青年

特殊的conditon

各种空值(空字符串、空列表等)作用等同于False
各种非空值，作用等同于True

a = None

if a:
    print('a是非空数据')
else:
    print('a是空数据')

a是空数据

for循环

重复做某件事
迭代出数据中的内容(元素)

上面这个图可以解读为

我们想对iterable这个集合中的每一个item:

做点事(对item做操作)

重复做某事

问题1

计算1+2+3+…+97+98+99+100=?

1 + 2 = 3 3 + 3 = 6 6 + 4 = 10 10 + 5 = 15

result = 0

#int
for i in range(1, 101):
    result = result + i
    
print(result)

迭代出数据中的内容

从某种“集合”（这个“集合”可以使list、set、tuple等），只要“集合”内部有多个成员就可以使用for循环迭代出内部的成员

names = ['David', 'Henry', 'Mary']

for name in names:
    print(name)

David
Henry
Mary

name = 'David'

for s in name:
    print(s)

D
a
v
i
d

infos =  {'David':{'age':25, 
                   'gender':'Male'},
          'Mary':{'age':23,
                  'gender': 'Female'},
          'Henry':{'age':23,
                  'gender': 'Male'}
         }

for item in infos.items():
    print(item)

('David', {'age': 25, 'gender': 'Male'})
('Mary', {'age': 23, 'gender': 'Female'})
('Henry', {'age': 23, 'gender': 'Male'})

for name, info in infos.items():
    print(name, info)

David
Mary
Henry

try-except

遇到无关紧要的bug，不会停下来，让程序有一定的容错能力。通俗点就是此处不留爷，自有留爷处，凡事别钻牛角尖。

for x in [1,2,0,2,1]:
    print(10/x)

10.0
5.0
---------------------------------------------------------------------------

ZeroDivisionError                         Traceback (most recent call last)

<ipython-input-19-83bea9c92c0e> in <module>
      1 for x in [1,2,0,2,1]:
----> 2     print(10/x)
ZeroDivisionError: division by zero

for x in [1,2,0,2,1]:
    try:
        print(10/x)
    except:
        print('0除错误')
        #pass

10.0
5.0
0除错误
5.0
10.0

练习1

假设现在某人的能力为1，每天比前一天进步0.01，一年后他的能力是多少？

ability = 1
scale = 1.01

records = []
for i in range(365):
    ability = ability * 1.01
    records.append(ability)
    
print(records)

[1.01, 1.0201, 1.030301, 1.04060401, 1.0510100501, 1.061520150601, 1.0721353521070098, 1.08285670562808, 1.0936852726843609, 1.1046221254112045, 1.1156683466653166, ...................36.30913774096189, 36.672229118371504, 37.03895140955522, 37.40934092365077, 37.783434332887275]

import matplotlib.pyplot as plt
import math
%matplotlib inline

ability = 1
scale = 1.02
records = []

days = range(1, 365)
for day in days:
    ability = ability*scale
    records.append(ability)
 

plt.plot(days, records)
plt.title('Be better everyday!')

Text(0.5, 1.0, 'Be better everyday!')

安装包的方法

命令行执行 pip install packagename
jupyter notebook的Cell中执行!pip install packagename
如果是mac，pip写成pip3

!pip install matplotlib

Looking in indexes: https://mirrors.aliyun.com/pypi/simple/
Requirement already satisfied: matplotlib in c:\users\thunderhit\appdata\local\programs\python\python37-32\lib\site-packages (3.2.1)
Requirement already satisfied: kiwisolver>=1.0.1 in c:\users\thunderhit\appdata\local\programs\python\python37-32\lib\site-packages (from matplotlib) (1.2.0)
Requirement already satisfied: python-dateutil>=2.1 in c:\users\thunderhit\appdata\local\programs\python\python37-32\lib\site-packages (from matplotlib) (2.8.1)
Requirement already satisfied: cycler>=0.10 in c:\users\thunderhit\appdata\local\programs\python\python37-32\lib\site-packages (from matplotlib) (0.10.0)
Requirement already satisfied: numpy>=1.11 in c:\users\thunderhit\appdata\local\programs\python\python37-32\lib\site-packages (from matplotlib) (1.18.2)
Requirement already satisfied: pyparsing!=2.0.4,!=2.1.2,!=2.1.6,>=2.0.1 in c:\users\thunderhit\appdata\local\programs\python\python37-32\lib\site-packages (from matplotlib) (2.4.7)
Requirement already satisfied: six>=1.5 in c:\users\thunderhit\appdata\local\programs\python\python37-32\lib\site-packages (from python-dateutil>=2.1->matplotlib) (1.14.0)

练习2

打印九九乘法表格

用到的知识点:

for循环
字符串format方法
print函数(涉及到end参数)

for row in range(1, 10):
    #print(row)
    for col in range(1, row+1):
        formula = '{col}*{row}={res}'.format(col=col, row=row, res=col*row)
        print(formula, end='\t')
    print('')

1*1=1	
1*2=2	2*2=4	
1*3=3	2*3=6	3*3=9	
1*4=4	2*4=8	3*4=12	4*4=16	
1*5=5	2*5=10	3*5=15	4*5=20	5*5=25	
1*6=6	2*6=12	3*6=18	4*6=24	5*6=30	6*6=36	
1*7=7	2*7=14	3*7=21	4*7=28	5*7=35	6*7=42	7*7=49	
1*8=8	2*8=16	3*8=24	4*8=32	5*8=40	6*8=48	7*8=56	8*8=64	
1*9=9	2*9=18	3*9=27	4*9=36	5*9=45	6*9=54	7*9=63	8*9=72	9*9=81

help(print)

Help on built-in function print in module builtins:

print(...)
    print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False)
    
    Prints the values to a stream, or to sys.stdout by default.
    Optional keyword arguments:
    file:  a file-like object (stream); defaults to the current sys.stdout.
    sep:   string inserted between values, default a space.
    end:   string appended after the last value, default a newline.
    flush: whether to forcibly flush the stream.

for row in range(1, 10):
    for col in range(1, row+1):
        formula = '{col}*{row}={res}'
        content = formula.format(col=col, row=row, res=col*row)
        print(content, end='\t')
    print()

1*1=1	
1*2=2	2*2=4	
1*3=3	2*3=6	3*3=9	
1*4=4	2*4=8	3*4=12	4*4=16	
1*5=5	2*5=10	3*5=15	4*5=20	5*5=25	
1*6=6	2*6=12	3*6=18	4*6=24	5*6=30	6*6=36	
1*7=7	2*7=14	3*7=21	4*7=28	5*7=35	6*7=42	7*7=49	
1*8=8	2*8=16	3*8=24	4*8=32	5*8=40	6*8=48	7*8=56	8*8=64	
1*9=9	2*9=18	3*9=27	4*9=36	5*9=45	6*9=54	7*9=63	8*9=72	9*9=81

了解课程

点击进入详情页

Python语法入门-课件下载#

if条件判断#

condition为布尔值、布尔运算、成员运算符#

特殊的conditon#

for循环#

上面这个图可以解读为#

重复做某事#

问题1#

迭代出数据中的内容#

try-except#

练习1#

安装包的方法#

练习2#

了解课程#