python入门合集：

python快速入门【一】-----基础语法

IPython/Jupyter

IPython Notebook号称 “编码器的实验室笔记本” - 允许用户在单个基于浏览器的页面中交叉显示/执行数据，代码和说明文本，而不是在单独的文件中

基础类型

python中的主要基本数据类型是数字（整数和浮点数），布尔值和字符串

Hello World!

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# This is a one line comment

print('Hello World!')

Hello World!

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# Strings can be enclosed by ',", or """

print("Hello World!")

Hello World!

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# \ is used as a escape character.

# There are many special escape sequences

# Notable are: \t (tab)

#             \n (new line)

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print("The \n makes a new line")

The

 makes a new line

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print("The \t is a tab")

The 	 is a tab

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print('I\'m going to the movies')

I'm going to the movies

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# Using \ to not accidently close the string by having a closing "

print("This is a string enclosed by \"\" not '' ")

This is a string enclosed by "" not ''

In [3]

# Creating a variable

# Variables are used to store information to be referenced

# and manipulated in a computer program.

firstVariable = 'Hello World'

print(firstVariable)

Hello World

字符串操作

字符串是python的特殊类型。作为对象，在类中，您可以使用.methodName（）表示法调用字符串对象上的方法。字符串类在python中默认可用，因此您不需要import语句即可将对象接口用于字符串。

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# go over ? mark after if you are not sure what method does.

print(firstVariable.lower())

print(firstVariable.upper())

print(firstVariable.title())

hello world

HELLO WORLD

Hello World

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# To look up what each method does

firstVariable.lower?

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# Can also use help

help(firstVariable.lower)

Help on built-in function lower:

lower(...)

    S.lower() -> string

    Return a copy of the string S converted to lowercase.

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help

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firstVariable.split(' ')

['Hello', 'World']

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a=firstVariable.split(' ')

a

['Hello', 'World']

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' '.join(a)

'Hello World'

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print("0" + "1")

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"0" * 3

'000'

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# You can add strings together.

"Fizz" + "Buzz"

'FizzBuzz'

基础数学

有四种不同的数字类型：普通整数，长整数，浮点数和复数。另外，布尔值是普通整数的子类型。

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# Addition, add two int together

1+1

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# if one of the operands is a float, the result is a float.

130-2.0

128.0

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130-2

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# integer division

130/2

65.0

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130.0/2

65.0

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# Multiplication

2*3

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# Exponentiation **

# This operator raises the number to its left to the power of the number to its right

2**3

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# Modulo

# Returns the remainder of the division of the number to the left by the

# number on its right.

9%3

if 语句

比较操作符	功能
<	小于
<=	小于或等于

| 大于 = | 大于或等于 == | 等于 != | 不等于

检查某些东西是否为True，如果是，则执行此操作。如果它不是True（False），则不执行

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# Notice you have to indent after you start a if statement.

num = 3

if num == 3:

    print(num)

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# Nothing is outputted because num > 10 is FALSE

num = 3

if num > 10:

    print(num)

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num = 3

if num % 3 == 0:

    print("Fizz")

Fizz

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num = 10

if num % 5 == 0:

    print("Buzz")

Buzz

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if True:

    print("This was True")

This was True

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if False:

    print("Nothing printed")

逻辑操作符	描述
and	如果两个操作数均为True，则condition变为True.
or	如果两个操作数中的任何一个为True，则condition变为True.
not	用于反转逻辑（不是False变为True，而不是True变为False

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num = 4

num > 0 and num  < 15

True

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# both the conditions are true, so the num will be printed out

if num > 0 and num  < 15:

    print(num)

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# num > 0 is True, num > 15 is False

# Since the first condition is True, it is True

num = 4

num > 0 or num  > 15

True

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if num > 0 or num  > 15:

    print(num)

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# or will only evaluate to False if both are False

if False or False:

    print('Nothing will print out')

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num = 10

not num < 20

False

else 语句

必须在if或elif语句之后。最多可以有一个其他声明。仅当上面的所有“if”和“elif”语句都为False时才会执行

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num = 1

if num > 3 :

    print("Hi")

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"""We will execute what is inside the else statement

because num is not greater than 3

"""

num = 1

if num > 3 :

    print("Hi")

else:

    print("number is not greater than 3")

number is not greater than 3

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"""We will execute what is inside the if statement because num > 4"""

num = 4

if num > 3 :

    print("Hi")

else:

    print("number is not greater than 3")

Hi

Task

将num分配给整数值。
如果整数是偶数，写一个if else组合将打印“你的整数是偶数”。否则，打印“你的整数是奇数”。

提示：任何可以精确地除以2的整数都是偶数（例如：2,4,6）。任何不能精确地除以2的整数都是奇数（例如：1,3,5）。使用模运算符（％），它将数字左边的余数除以右边的数字。

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num = 3

if num % 2 == 0:

    print("Your integer is even")

else:

    print("Your integer is odd")

Your integer is odd

elif 语句

必须在if语句之后。 elif语句语句允许您检查True的多个表达式，并在其中一个条件求值为True时立即执行代码块。

与else类似，elif语句是可选的。但是，与其他情况不同，最多只能有一个语句，if后面可以有任意数量的elif语句。

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num = 21

if num > 50:

    print('num is larger than 50')

elif num == 21:

    print('num = 21')

else:

    print('Catchall condition')

num = 21

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my_num = 5

if my_num % 2 == 0:

    print("Your number is even")

elif my_num % 2 != 0:

    print("Your number is odd")

else:

    print("Are you sure your number is an integer?")

Your number is odd

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# You can have mulitple elif statements.

# Remember only the first True statement has its block of code executed. 

dice_value = 1

if dice_value == 1:

    print('You rolled a {}. Great job!'.format(dice_value))

elif dice_value == 2:

    print('You rolled a {}. Great job!'.format(dice_value))

elif dice_value == 3:

    print('You rolled a {}. Great job!'.format(dice_value))

elif dice_value == 4:

    print('You rolled a {}. Great job!'.format(dice_value))

elif dice_value == 5:

    print('You rolled a {}. Great job!'.format(dice_value))

elif dice_value == 6:

    print('You rolled a {}. Great job!'.format(dice_value))

else:

    print('None of the conditions above (if elif) were evaluated as True')

You rolled a 1. Great job!

Task

将num分配给整数值。
编写一系列if，elif，else语句，打印您指定的num。但是对三的倍数要打印“Fizz”而不是数字, 五的倍数要打印“Buzz”。对于三和五共同的倍数则打印“FizzBuzz”

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# Solution 1

num = 10

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if num % 3 == 0 and num % 5 == 0:

    print('FizzBuzz')

elif num % 3 == 0:

    print('Fizz')

elif num % 5 == 0:

    print('Buzz')

else:

    print(str(num))

Buzz

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# Solution 2

num = 15

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"""Notice how difficult this solution is relative to Solution 1"""

string = ""

if num % 3 == 0:

    string = string + "Fizz"

if num % 5 == 0:

    string = string + "Buzz"

if num % 5 != 0 and num % 3 != 0:

    string = string + str(num)

print(string)

FizzBuzz

列表

列表后面要加上方括号 [ ]

| | | | --- | --- | --- | --- | --- z =| [3, | 7, | 4, | 2] index | 0 | 1 | 2 | 3

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# Defining a list

z = [3, 7, 4, 2]

访问列表里面的值

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# The first element of a list is at index 0

z[0]

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z[2]

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# Access Last Element of List

z[-2]

切分列表

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# first index is inclusive (before the :) and last (after the :) is not.

# not including index 2

z[0:2]

[3, 7]

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# everything up to index 3

z[:3]

[3, 7, 4]

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# index 1 to end of list

z[1:]

[7, 4, 2]

取列表的最大值, 最小值, 长度, 以及总和

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print(min(z), max(z), len(z), sum(z))

2 7 4 16

对列表中对象出现次数进行统计

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random_list = [4, 1, 5, 4, 10, 4]

random_list.count(4)

返回列表第一个指针

| | | | | | --- | --- | --- | --- | --- | --- | --- random_list =| [4, | 1, | 5, | 4, | 10, | 4] index=| 0 | 1 | 2 | 3 | 4 | 5

In [9]

random_list.index(4)

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# you can specify where you start your search

random_list.index(4, 3)

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# random_list.index(value, [start, stop])

random_list.index(4, 5, 6)

对列表进行排序

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x = [3, 7, 2, 11, 8, 10, 4]

y = ['Steve', 'Rachel', 'Michael', 'Adam', 'Monica', 'Jessica', 'Lester']

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# Sorting and Altering original list

# low to high

x.sort()

print(x)

[2, 3, 4, 7, 8, 10, 11]

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# Sorting and Altering original list

# high to low

x.sort(reverse = True)

print(x)

[11, 10, 8, 7, 4, 3, 2]

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# Sorting and Altering original list

# A-Z

y.sort()

print(y)

['Adam', 'Jessica', 'Lester', 'Michael', 'Monica', 'Rachel', 'Steve']

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# Sorting and Altering original list

# Z-A

y.sort(reverse = True)

print(y)

['Steve', 'Rachel', 'Monica', 'Michael', 'Lester', 'Jessica', 'Adam']

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# sorting list WITHOUT altering original list

new_list = sorted(y)

new_list

['Adam', 'Jessica', 'Lester', 'Michael', 'Monica', 'Rachel', 'Steve']

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# notice y is unchanged

y

['Steve', 'Rachel', 'Monica', 'Michael', 'Lester', 'Jessica', 'Adam']

在列表结尾添加一个对象

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[11, 10, 8, 7, 4, 3, 2]

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x.append(3)

print(x)

[11, 10, 8, 7, 4, 3, 2, 3]

删除列表中一个对象

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x.remove(10)

print(x)

[11, 8, 7, 4, 3, 2, 3]

删除列表中指定位置的对象

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# List before you remove an item

print(x)

[11, 8, 7, 4, 3, 2, 3]

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# Remove item at the index

# this function will also return the item you removed from the list

# Default is the last index

x.pop(3)

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print(x)

[11, 8, 7, 3, 2, 3]

合并列表

通过在末尾续加的方式来延长列表

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x.extend([4, 5])

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[11, 8, 7, 3, 2, 3, 4, 5]

In [195]

# lists can be diverse, each element in the list can be of a different type.

# lists are really list of pointers, and these pointers can

# point to anything.

# Concatenating Lists

print('x+y=',x+y)

x+y= [11, 8, 7, 3, 2, 3, 4, 5, 'Steve', 'Rachel', 'Monica', 'Michael', 'Lester', 'Jessica', 'Adam']

在列表指定位置前插入对象

In [30]

[11, 8, 7, 3, 2, 3, 4, 5]

In [197]

x.insert(4, [4, 5])

In [198]

[11, 8, 7, 3, [4, 5], 2, 3, 4, 5]