Python数据分析_第01课：Python概览_笔记变量类型运算符
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变量类型
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打印
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行和缩进
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多行语句
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引号
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注释
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空行
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码组
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帮助
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变量赋值
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数字
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删除
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字符串
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列表
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元组
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字典
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运算符
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比较运算符
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赋值运算符
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位运算符
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逻辑运算符
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成员运算符
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身份运算符
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运算符优先级
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GitHub:
变量类型
打印
# 打印
print("Hello, Python!")
Hello, Python!
行和缩进
# 行和缩进
if True:
print("True")
else:
print("False")
True
if True:
print("Answer")
print("True")
else:
print("Answer")
# 没有严格缩进，在执行时报错
print("False")
File "<ipython-input-3-d9287ace04e4>", line 7
print("False")
^
IndentationError: unexpected indent
多行语句
# 多行语句
item_one = 1
item_two = 2
item_three = 3
total = item_one + \
item_two + \
item_three
print(total)
6
days = ['Monday', 'Tuesday', 'Wednesday',
'Thursday', 'Friday']
days
['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']
引号
# 引号
word = 'word'
sentence = "这是一个句子。"
paragraph = """这是一个段落。
包含了多个语句"""
print(word)
print(sentence)
print(paragraph)
word
这是一个句子。
这是一个段落。
包含了多个语句
注释
# 注释
# 第一个注释
print("Hello, Python!") # 第二个注释
name = "Madisetti" # 这是一个注释
'''
这是多行注释，使用单引号。
这是多行注释，使用单引号。
这是多行注释，使用单引号。
'''
"""
这是多行注释，使用双引号。
这是多行注释，使用双引号。
这是多行注释，使用双引号。
"""
空行
# 空行
eval(input("\n\nPress the enter key to exit."))
import sys
x = 'foo'
sys.stdout.write(x + '\n')
foo
码组
# 码组
'''
if expression :
suite
elif expression :
suite
else :
suite
'''
帮助
# 帮助
help(sys.stdout.write)
Help on method write in module ipykernel.iostream:
write(string) method of ipykernel.iostream.OutStream instance
Write string to stream.
Returns the number of characters written (which is always equal to
the length of the string).
变量赋值
# 变量赋值
counter = 100 # 赋值整型变量
miles = 1000.0 # 浮点型
name = "John" # 字符串
print(counter)
print(miles)
print(name)
a = b = c = 1
print(a, b, c)
a, b, c = 1, 2, "john"
print(a, b, c)
100
1000.0
John
1 1 1
1 2 john
数字
# 数字
var1 = 1
var2 = 10
删除
# 删除 del var1[,var2[,var3[....,varN]]]]
var = 5896419821
var_a = 0.22
var_b = 3e2
del var
del var_a, var_b
字符串
# 字符串
# s="a1a2•••an"(n>=0)
s = 'ilovepython'
print((s[1:5]))
print((s[5:-1]))
str = 'Hello World!'
print(str) # 输出完整字符串
print(str[0]) # 输出字符串中的第一个字符
print(str[2:5]) # 输出字符串中第三个至第五个之间的字符串
print(str[2:]) # 输出从第三个字符开始的字符串
print(str * 2) # 输出字符串两次
print(str + "TEST") # 输出连接的字符串
love
pytho
Hello World!
H
llo
llo World!
Hello World!Hello World!
Hello World!TEST
列表
# 列表
list = ['abcd', 786, 2.23, 'john', 70.2]
tinylist = [123, 'john']
print(list) # 输出完整列表
print(list[0]) # 输出列表的第一个元素
print(list[1:3]) # 输出第二个至第三个的元素
print(list[2:]) # 输出从第三个开始至列表末尾的所有元素
print(tinylist * 2) # 输出列表两次
print(list + tinylist) # 打印组合的列表
['abcd', 786, 2.23, 'john', 70.2]
abcd
[786, 2.23]
[2.23, 'john', 70.2]
[123, 'john', 123, 'john']
['abcd', 786, 2.23, 'john', 70.2, 123, 'john']
元组
# 元组
tuple = ('abcd', 786, 2.23, 'john', 70.2)
tinytuple = (123, 'john')
print(tuple) # 输出完整元组
print(tuple[0]) # 输出元组的第一个元素
print(tuple[1:3]) # 输出第二个至第三个的元素
print(tuple[2:]) # 输出从第三个开始至列表末尾的所有元素
print(tinytuple * 2) # 输出元组两次
print(tuple + tinytuple) # 打印组合的元组
tuple = ('abcd', 786, 2.23, 'john', 70.2)
list = ['abcd', 786, 2.23, 'john', 70.2]
tuple[2] = 1000 # 元组中是非法应用
list[2] = 1000 # 列表中是合法应用
('abcd', 786, 2.23, 'john', 70.2)
abcd
(786, 2.23)
(2.23, 'john', 70.2)
(123, 'john', 123, 'john')
('abcd', 786, 2.23, 'john', 70.2, 123, 'john')
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-17-db0548b12b81> in <module>()
12 tuple = ('abcd', 786, 2.23, 'john', 70.2)
13 list = ['abcd', 786, 2.23, 'john', 70.2]
---> 14 tuple[2] = 1000 # 元组中是非法应用
15 list[2] = 1000 # 列表中是合法应用
TypeError: 'tuple' object does not support item assignment
字典
# 字典
dict = {}
dict['one'] = "This is one"
dict[2] = "This is two"
tinydict = {'name': 'john', 'code': 6734, 'dept': 'sales'}
print(dict['one']) # 输出键为'one' 的值
print(dict[2]) # 输出键为 2 的值
print(tinydict) # 输出完整的字典
print(list(tinydict.keys())) # 输出所有键
print(list(tinydict.values())) # 输出所有值
运算符
算术运算符
# 算术运算符
a = 21
b = 10
c = 0
c = a + b
print("Line 1 - Value of c is ", c)
c = a - b
print("Line 2 - Value of c is ", c)
c = a * b
print("Line 3 - Value of c is ", c)
c = a / b
print("Line 4 - Value of c is ", c)
c = a % b
print("Line 5 - Value of c is ", c)
a = 2
b = 3
c = a ** b
print("Line 6 - Value of c is ", c)
a = 10
b = 5
c = a // b
print("Line 7 - Value of c is ", c)
Line 1 - Value of c is 31
Line 2 - Value of c is 11
Line 3 - Value of c is 210
Line 4 - Value of c is 2.1
Line 5 - Value of c is 1
Line 6 - Value of c is 8
Line 7 - Value of c is 2
比较运算符
# 比较运算符
a = 21
b = 10
c = 0
if (a == b):
print("Line 1 - a is equal to b")
else:
print("Line 1 - a is not equal to b")
if (a != b):
print("Line 2 - a is not equal to b")
else:
print("Line 2 - a is equal to b")
if (a != b):
print("Line 3 - a is not equal to b")
else:
print("Line 3 - a is equal to b")
if (a < b):
print("Line 4 - a is less than b")
else:
print("Line 4 - a is not less than b")
if (a > b):
print("Line 5 - a is greater than b")
else:
print("Line 5 - a is not greater than b")
a = 5
b = 20
if (a <= b):
print("Line 6 - a is either less than or equal to b")
else:
print("Line 6 - a is neither less than nor equal to b")
if (b >= a):
print("Line 7 - b is either greater than or equal to b")
else:
print("Line 7 - b is neither greater than nor equal to b")
Line 1 - a is not equal to b
Line 2 - a is not equal to b
Line 3 - a is not equal to b
Line 4 - a is not less than b
Line 5 - a is greater than b
Line 6 - a is either less than or equal to b
Line 7 - b is either greater than or equal to b
赋值运算符
# 赋值运算符
a = 21
b = 10
c = 0
c = a + b
print("Line 1 - Value of c is ", c)
c += a
print("Line 2 - Value of c is ", c)
c *= a
print("Line 3 - Value of c is ", c)
c /= a
print("Line 4 - Value of c is ", c)
c = 2
c %= a
print("Line 5 - Value of c is ", c)
c **= a
print("Line 6 - Value of c is ", c)
c //= a
print("Line 7 - Value of c is ", c)
Line 1 - Value of c is 31
Line 2 - Value of c is 52
Line 3 - Value of c is 1092
Line 4 - Value of c is 52.0
Line 5 - Value of c is 2
Line 6 - Value of c is 2097152
Line 7 - Value of c is 99864
位运算符
# 位运算符
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
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)
Line 1 - Value of c is 12
Line 2 - Value of c is 61
Line 3 - Value of c is 49
Line 4 - Value of c is -61
Line 5 - Value of c is 240
Line 6 - Value of c is 15
逻辑运算符
# 逻辑运算符
a = 10
b = 20
c = 0
if (a and b):
print("Line 1 - a and b are true")
else:
print("Line 1 - Either a is not true or b is not true")
if (a or b):
print("Line 2 - Either a is true or b is true or both are true")
else:
print("Line 2 - Neither a is true nor b is true")
a = 0
if (a and b):
print("Line 3 - a and b are true")
else:
print("Line 3 - Either a is not true or b is not true")
if (a or b):
print("Line 4 - Either a is true or b is true or both are true")
else:
print("Line 4 - Neither a is true nor b is true")
if not (a and b):
print("Line 5 - Either a is not true or b is not true or both are not true")
else:
print("Line 5 - a and b are true")
Line 1 - a and b are true
Line 2 - Either a is true or b is true or both are true
Line 3 - Either a is not true or b is not true
Line 4 - Either a is true or b is true or both are true
Line 5 - Either a is not true or b is not true or both are not true
成员运算符
# 成员运算符
a = 10
b = 20
list = [1, 2, 3, 4, 5]
if (a in list):
print("Line 1 - a is available in the given list")
else:
print("Line 1 - a is not available in the given list")
if (b not in list):
print("Line 2 - b is not available in the given list")
else:
print("Line 2 - b is available in the given list")
a = 2
if (a in list):
print("Line 3 - a is available in the given list")
else:
print("Line 3 - a is not available in the given list")
Line 1 - a is not available in the given list
Line 2 - b is not available in the given list
Line 3 - a is available in the given list
身份运算符
# 身份运算符
a = 20
b = 20
if (a is b):
print("Line 1 - a and b have same identity")
else:
print("Line 1 - a and b do not have same identity")
if (id(a) == id(b)):
print("Line 2 - a and b have same identity")
else:
print("Line 2 - a and b do not have same identity")
b = 30
if (a is b):
print("Line 3 - a and b have same identity")
else:
print("Line 3 - a and b do not have same identity")
if (a is not b):
print("Line 4 - a and b do not have same identity")
else:
print("Line 4 - a and b have same identity")
Line 1 - a and b have same identity
Line 2 - a and b have same identity
Line 3 - a and b do not have same identity
Line 4 - a and b do not have same identity
运算符优先级
# 运算符优先级
a = 20
b = 10
c = 15
d = 5
e = 0
e = (a + b) * c / d # ( 30 * 15 ) / 5
print("Value of (a + b) * c / d is ", e)
e = ((a + b) * c) / d # (30 * 15 ) / 5
print("Value of ((a + b) * c) / d is ", e)
e = (a + b) * (c / d) # (30) * (15/5)
print("Value of (a + b) * (c / d) is ", e)
e = a + (b * c) / d # 20 + (150/5)
print("Value of a + (b * c) / d is ", e)
Value of (a + b) * c / d is 90.0
Value of ((a + b) * c) / d is 90.0
Value of (a + b) * (c / d) is 90.0
Value of a + (b * c) / d is 50.0
参考资料：炼数成金Python数据分析课程
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