python：为什么替换不起作用？

Question

我编写了一个快速脚本，以从保存在excel列中的网站地址列表中删除“ http：//”子字符串。该函数替换，但是不起作用，我也不明白为什么。

from openpyxl import load_workbook

def rem(string):
    print string.startswith("http://")    #it yields "True"
    string.replace("http://","")
    print string, type(string)    #checking if it works (it doesn't though, the output is the same as the input)

wb = load_workbook("prova.xlsx")
ws = wb["Sheet"]

for n in xrange(2,698):
    c = "B"+str(n)
    print ws[c].value, type(ws[c].value)   #just to check value and type (unicode)
    rem(str(ws[c].value))    #transformed to string in order to make replace() work

wb.save("prova.xlsx")    #nothing has changed

Answer 1

string.replace(old, new[, max])只返回一个值\xe2\x80\x94，它不会修改string. 例如，

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>>> a = "123"\n>>> a.replace("1", "4")\n\'423\'\n>>> a\n\'123\'\n

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您必须将字符串重新分配给其修改后的值，如下所示：

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>>> a = a.replace("1", "4")\n>>> a\n\'423\'\n

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所以在你的情况下，你会想写

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string = string.replace("http://", "")\n

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Answer 2

String.replace(substr)

没有就位，请将其更改为：

string = string.replace("http://","")