I've run some tests here and I think I've found the answer.

My var self.name has a <class 'PyQt4.QtCore.QString'> type, since I'm getting it from a QtWidget. Someone, please, correct me if I'm wrong but from the tests I run and from the docs (http://doc.qt.io/qt-5/qstring.html#replace) it seems that the replace method in <class 'PyQt4.QtCore.QString'> happens inplace. Whereas for the Python str, it does not since python strings are immutable.

So, in short:

• Python str: inplace=False (Python strings are immutable)
• PyQt4.QtCore.QString: inplace=True

Anyway, hope this can be helpful

You're iterating through the elements within the DataFrame, in which case I'm assuming it's type str (or being coerced to str when you replace). str.replace doesn't have an argument for inplace=....

You should be doing this instead:

dataset['ver'] = dataset['ver'].str.replace('.', '')

Don't use a string, use something mutable like bytearray:

#!/usr/bin/python

s = bytearray("my dog has fleas")
for n in xrange(len(s)):
    s[n] = chr(s[n]).upper()
print s

Results in:

MY DOG HAS FLEAS

Edit:

Since this is a bytearray, you aren't (necessarily) working with characters. You're working with bytes. So this works too:

s = bytearray("\x81\x82\x83")
for n in xrange(len(s)):
    s[n] = s[n] + 1
print repr(s)

gives:

bytearray(b'\x82\x83\x84')

If you want to modify characters in a Unicode string, you'd maybe want to work with memoryview, though that doesn't support Unicode directly.

Because .replace('=', '') requires the cell value to be exactly '=' which is obviously not true in your case.

You may instead use it with regex:

df = pd.DataFrame({'a': ['="abc"', '="bcd"'], 'b': ['="uef"', '="hdd"'], 'c':[1,3]})
df.replace([r'^="', r'"$'], '', regex=True, inplace=True)
print(df)

     a    b  c
0  abc  uef  1
1  bcd  hdd  3

Two regular expressions are used here, with the first taking care of the head and the second the tail.

You can create the function create_frame without inplace=True.

if you use inplace=True, it will return None from the func create_frame.

similarly, Pandas dataframe: set_index with inplace=True returns a NoneType, why??

import pandas as pd

def create_frame(path):
    df1 = pd.read_excel(path)
    return df1.replace(('Visit 2: Day 1','Day 1'))

df = create_frame('example.xlsx')
df.to_csv('test.csv')

when you use df2 = df1.replace(('Visit 2: Day 1','Day 1')), it will not affect df1.

so without use func, you can do like this:

df1 = pd.read_excel(path)
df2 = df1.replace(('Visit 2: Day 1','Day 1'))
df2.to_csv('test.csv')

df1 = pd.read_excel(path)
df1.replace(('Visit 2: Day 1','Day 1'), inplace=True)
df1.to_csv('test.csv')

Use fileinput.FileInput, with inplace=True. printed line will be used as a replacement string for each line.

myfile = fileinput.FileInput("inputRegex.txt", inplace=True)

for line in myfile:
    line = re.sub(r"[+-]? *(?:\d+(?:\.\d*)?|\.\d+)(?:[eE][+-]?\d+)?",
                  "foundValue",
                  line.rstrip())
    print(line)

UPDATE

re.sub can accept a function as replacement. It will be called with match object and the return value of the function is used as a replacement string.

The following is slightly modified version to use captured groups (to use in replacement function).

line = re.sub(r"([+-]? *)(\d+(?:\.\d*)?|\.\d+)([eE][+-]?\d+)?",
              lambda m: m.group(1) + re.sub('(\..{4}).*', r'\1', m.group(2)) + (m.group(3) or ''),
              line.rstrip())