Python基本操作

1.文件读取与写入

• with open(somefile) as f,是比较推荐的读取文件时的字段，可自动关闭文件，避免因为程序崩溃未及时写入；
• 内置函数readlines，读取后，文件内容以列表的格式返回；

with open('D:/tmp/info.txt') as f:
    p1 = f.readlines()
    print(p1)
with open('D:/tmp/info1.txt'，w) as f:
   f.writelines(p1)

• read,读取后，文件内容以一个字符串的形式返回：

with open('D:/tmp/info.txt') as f:
    p2 = f.read()
    print(p2)
with open('D:/tmp/info2.txt'，w) as f:
   f.writelines(p2)

• pandas中的read_table函数和read_csv函数，pandas包对R用户比较友好，读取后为数据框，就相当于R中的read.table，read.csv函数;

import pandas as pd
with open('D:/tmp/info.txt') as f:
        p3 = pd.read_table(f)
        print(p3)
p3.to_csv('D:/tmp/info3.txt')

2.字符串操作

import re

a = ['Joey','Pheebe','Monica','Chandeler','Rachel','Ross']

####split和join的使用

b = ','.join(a)

'Hi '+a[0]
Out[78]: 'Hi Joey'

print(a)
['Joey', 'Pheebe', 'Monica', 'Chandeler', 'Rachel', 'Ross']

print(b)
Joey,Pheebe,Monica,Chandeler,Rachel,Ross

b.split(',')
Out[81]: ['Joey', 'Pheebe', 'Monica', 'Chandeler', 'Rachel', 'Ross']

#####判断字符串的有无，[]是模板的作用（？）

[re.search('Ph',x) for x in a]
Out[83]: [None, <re.Match object; span=(0, 2), match='Ph'>, None, None, None, None]

['Ph' in x for x in a]
Out[84]: [False, True, False, False, False, False]

#####字符串替换

seq =  'ACGTACCTA'
###table即所制定的变换的规则
table = str.maketrans('AT','TA')

seq.translate(table)
Out[88]: 'TCGATCCAT'

seq.replace('AC', 'TG')
Out[89]: 'TGGTTGCTA'