[Python] Global variables failed to update globally

I'm writing a script buy_strategy1 containing global variables and the script is called as function by the main program. The global variabls in the script buy_strategy1 are variables initialized in the main program. When the program is running, it is supposed to update the global variables count_1min_goal and hold in the main program if speific criterions are satisfied.

The main program is as follows:

#%% main program

# parameters-------------------------------------------------------------------
n = 5
m1 = 5
m2 = 10
m3 = 20
n1 = 8
count = 0

count_1min_goal = 0 # initialized and waiting for updating
hold = False # initialized and waiting for updating


# start strategy---------------------------------------------------------------

for idx1 in range(0,len(df)+1,n):


if count==70:break
count += 1

df_temp = df.iloc[n-1:idx1:n].copy()

for idx2 in range(idx1,idx1+3):

if hold is False: # no position

try:

df_temp = get_current_candle(df, df_temp, idx2)
buy_strategy1(df_1min, df_temp, idx2)

except Exception:
pass


The script is:

import pandas_ta as ta
def buy_strategy1(df_1min, df_n_min, idx, m1=5, m2=10, m3=20, n1=8, n_calc=100):

global count_1min_goal, hold

ma1 = ta.sma(df_n_min['Close'],length=m1)
ma2 = ta.sma(df_n_min['Close'],length=m2)
ma3 = ta.sma(df_n_min['Close'],length=m3)


if df_n_min.iloc[-1]['Close']<min(ma1.iloc[-1], ma2.iloc[-1], ma3.iloc[-1]):

corr_1min = df_1min.iloc[idx-n_calc:idx+1] # part of 1min dataframe

ma_1min = ta.sma(corr_1min['Close'],length=n1) # calculate ma for 1 min

if corr_1min['Close'].iloc[-1] > ma_1min.iloc[-1]:
count_1min_goal += 1
else:
count_1min_goal = 0

if count_1min_goal == 2: # 2 consecutive 1 min candle above ma
hold = True # open a position

print('count_1min_goal=' + str(count_1min_goal))
print('hold=' + str(hold))


It can be seen in the script buy_strategy1 that count_1min_goal and hold should be updated when the criterions are satisfied. When the program is running, it printed the following information as expected:

count_1min_goal=2
hold=True


That means that count_1min_goal and hold are updated successfully in the script. But in the main program it still gives

count_1min_goal=0
hold=False


I want to know why it failed to update the variables in the main program and how to fix it?

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